### Summary

If `dependencies` in `galaxy.yml` is defined but not assigned any value, the installation would fail.


Please note the `dependencies`.

The installation would fail.

```yml
namespace: my_namespace
name: my_collection
version: 1.0.0
readme: README.md
authors:
- your name <example@domain.com>
description: your collection description
license:
- GPL-2.0-or-later
license_file: ''
tags: []
dependencies:
repository: http://example.com/repository
documentation: http://docs.example.com
homepage: http://example.com
issues: http://example.com/issue/tracker
build_ignore: []
```

It works if `dependencies` is assigned to `{}`.

```yml
namespace: my_namespace
name: my_collection
version: 1.0.0
readme: README.md
authors:
- your name <example@domain.com>
description: your collection description
license:
- GPL-2.0-or-later
license_file: ''
tags: []
dependencies: {}
repository: http://example.com/repository
documentation: http://docs.example.com
homepage: http://example.com
issues: http://example.com/issue/tracker
build_ignore: []
```

### Issue Type

Bug Report

### Component Name

ansible-galaxy

### Ansible Version

```console
$ ansible --version
[WARNING]: You are running the development version of Ansible. You should only run Ansible from "devel" if you are modifying
the Ansible engine, or trying out features under development. This is a rapidly changing source of code and can become
unstable at any point.
ansible [core 2.14.0.dev0] (devel abdd237de7) last updated 2022/04/19 11:12:55 (GMT +800)
  config file = None
  configured module search path = ['/Users/jackzhang/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/jackzhang/src/github/ansible/lib/ansible
  ansible collection location = /Users/jackzhang/.ansible/collections:/usr/share/ansible/collections
  executable location = /Users/jackzhang/.pyenv/versions/v-397/bin/ansible
  python version = 3.9.7 (default, Oct 28 2021, 19:01:53) [Clang 12.0.5 (clang-1205.0.22.11)]
  jinja version = 3.1.1
  libyaml = True
```


### Configuration

```console
$ ansible-config dump --only-changed
CONFIG_FILE() = None
```


### OS / Environment

MacOS

### Steps to Reproduce

<!--- Paste example playbooks or commands between quotes below -->
```shell
$ ansible-galaxy collection init my_namespace.my_collection
$ cd my_namespace.my_collection
$ gsed -ri 's/^(dependencies:)(.*)$/\1/' galaxy.yml
$ ansible-galaxy collection install -vvv .
```


### Expected Results

I expect the `my_namespace.my_collection` with `dependencies=None` can be installed successfully

### Actual Results

```console
ansible-galaxy collection install -vvvv .
[WARNING]: You are running the development version of Ansible. You should only run Ansible from "devel" if you are modifying
the Ansible engine, or trying out features under development. This is a rapidly changing source of code and can become
unstable at any point.
ansible-galaxy [core 2.14.0.dev0] (devel abdd237de7) last updated 2022/04/19 11:12:55 (GMT +800)
  config file = None
  configured module search path = ['/Users/jackzhang/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/jackzhang/src/github/ansible/lib/ansible
  ansible collection location = /Users/jackzhang/.ansible/collections:/usr/share/ansible/collections
  executable location = /Users/jackzhang/.pyenv/versions/v-397/bin/ansible-galaxy
  python version = 3.9.7 (default, Oct 28 2021, 19:01:53) [Clang 12.0.5 (clang-1205.0.22.11)]
  jinja version = 3.1.1
  libyaml = True
No config file found; using defaults
Starting galaxy collection install process
Found installed collection geerlingguy.testing:1.0.0 at '/Users/jackzhang/.ansible/collections/ansible_collections/geerlingguy/testing'
Found installed collection lablabs.wireguard:0.1.1 at '/Users/jackzhang/.ansible/collections/ansible_collections/lablabs/wireguard'
[WARNING]: Collection at '/Users/jackzhang/.ansible/collections/ansible_collections/foo/bar' does not have a MANIFEST.json
file, nor has it galaxy.yml: cannot detect version.
Found installed collection foo.bar:* at '/Users/jackzhang/.ansible/collections/ansible_collections/foo/bar'
Found installed collection robertdebock.development_environment:2.1.1 at '/Users/jackzhang/.ansible/collections/ansible_collections/robertdebock/development_environment'
Found installed collection containers.podman:1.9.3 at '/Users/jackzhang/.ansible/collections/ansible_collections/containers/podman'
Found installed collection community.docker:2.3.0 at '/Users/jackzhang/.ansible/collections/ansible_collections/community/docker'
Found installed collection community.general:4.7.0 at '/Users/jackzhang/.ansible/collections/ansible_collections/community/general'
Found installed collection community.molecule:0.1.0 at '/Users/jackzhang/.ansible/collections/ansible_collections/community/molecule'
Process install dependency map
ERROR! Unexpected Exception, this is probably a bug: 'NoneType' object has no attribute 'items'
the full traceback was:

Traceback (most recent call last):
  File "/Users/jackzhang/src/github/ansible/lib/ansible/cli/__init__.py", line 601, in cli_executor
    exit_code = cli.run()
  File "/Users/jackzhang/src/github/ansible/lib/ansible/cli/galaxy.py", line 646, in run
    return context.CLIARGS['func']()
  File "/Users/jackzhang/src/github/ansible/lib/ansible/cli/galaxy.py", line 102, in method_wrapper
    return wrapped_method(*args, **kwargs)
  File "/Users/jackzhang/src/github/ansible/lib/ansible/cli/galaxy.py", line 1300, in execute_install
    self._execute_install_collection(
  File "/Users/jackzhang/src/github/ansible/lib/ansible/cli/galaxy.py", line 1328, in _execute_install_collection
    install_collections(
  File "/Users/jackzhang/src/github/ansible/lib/ansible/galaxy/collection/__init__.py", line 683, in install_collections
    dependency_map = _resolve_depenency_map(
  File "/Users/jackzhang/src/github/ansible/lib/ansible/galaxy/collection/__init__.py", line 1594, in _resolve_depenency_map
    return collection_dep_resolver.resolve(
  File "/Users/jackzhang/.pyenv/versions/3.9.7/envs/v-397/lib/python3.9/site-packages/resolvelib/resolvers.py", line 453, in resolve
    state = resolution.resolve(requirements, max_rounds=max_rounds)
  File "/Users/jackzhang/.pyenv/versions/3.9.7/envs/v-397/lib/python3.9/site-packages/resolvelib/resolvers.py", line 347, in resolve
    failure_causes = self._attempt_to_pin_criterion(name, criterion)
  File "/Users/jackzhang/.pyenv/versions/3.9.7/envs/v-397/lib/python3.9/site-packages/resolvelib/resolvers.py", line 207, in _attempt_to_pin_criterion
    criteria = self._get_criteria_to_update(candidate)
  File "/Users/jackzhang/.pyenv/versions/3.9.7/envs/v-397/lib/python3.9/site-packages/resolvelib/resolvers.py", line 198, in _get_criteria_to_update
    for r in self._p.get_dependencies(candidate):
  File "/Users/jackzhang/src/github/ansible/lib/ansible/galaxy/dependency_resolution/providers.py", line 425, in get_dependencies
    for dep_name, dep_req in req_map.items()
AttributeError: 'NoneType' object has no attribute 'items'
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
test_dir = to_bytes(tmp_path_factory.mktemp('test-ÅÑŚÌβŁÈ Collections Input'))
    json_data = b"not a json"
    tar_path = os.path.join(test_dir, b'ansible-collections.tar.gz')
    with tarfile.open(tar_path, 'w:gz') as tfile:
        b_io = BytesIO(json_data)
        tar_info = tarfile.TarInfo('MANIFEST.json')
        tar_info.size = len(json_data)
        tar_info.mode = 0o0644
        tfile.addfile(tarinfo=tar_info, fileobj=b_io)
    concrete_artifact_cm = collection.concrete_artifact_manager.ConcreteArtifactsManager(test_dir, validate_certs=False)
    expected = "Collection tar file member MANIFEST.json does not contain a valid json string."
    with pytest.raises(AnsibleError, match=expected):
        Requirement.from_requirement_dict({'name': to_text(tar_path)}, concrete_artifact_cm)
def test_build_requirement_from_name(galaxy_server, monkeypatch, tmp_path_factory):