### Summary

I have a task to conditionally install an SSH key on another machine:

```yaml
- authorized_key: ...
  delegate_to: "{{ jenkins_install_key_on }}"
  when: jenkins_install_key_on != ""
```

This works fine when `jenkins_install_key_on` is set to a non-blank value, but fails when `jenkins_install_key_on` is set to an empty string:

```
fatal: [jammy -> {{ jenkins_install_key_on }}]: FAILED! => {"msg": "Supplied entity must be Host or Group, got <class 'ansible.inventory.host.Host'> instead"}
```

It used to work with ansible-core 2.15 and older.

### Issue Type

Bug Report

### Component Name

delegate_to

### Ansible Version

```console
$ ansible --version
ansible [core 2.16.0]
  config file = /home/mg/src/deployments/provisioning/ansible.cfg
  configured module search path = ['/home/mg/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/mg/.local/pipx/venvs/ansible/lib/python3.11/site-packages/ansible
  ansible collection location = /home/mg/.ansible/collections:/usr/share/ansible/collections
  executable location = /home/mg/.local/bin/ansible
  python version = 3.11.6 (main, Oct  8 2023, 05:06:43) [GCC 13.2.0] (/home/mg/.local/pipx/venvs/ansible/bin/python)
  jinja version = 3.1.2
  libyaml = True
```


### Configuration

```console
# if using a version older than ansible-core 2.12 you should omit the '-t all'
$ ansible-config dump --only-changed -t all
ACTION_WARNINGS(/home/mg/src/deployments/provisioning/ansible.cfg) = False
CACHE_PLUGIN(/home/mg/src/deployments/provisioning/ansible.cfg) = jsonfile
CACHE_PLUGIN_CONNECTION(/home/mg/src/deployments/provisioning/ansible.cfg) = .cache/facts/
CACHE_PLUGIN_TIMEOUT(/home/mg/src/deployments/provisioning/ansible.cfg) = 86400
CALLBACKS_ENABLED(/home/mg/src/deployments/provisioning/ansible.cfg) = ['fancy_html']
CONFIG_FILE() = /home/mg/src/deployments/provisioning/ansible.cfg
DEFAULT_FORKS(/home/mg/src/deployments/provisioning/ansible.cfg) = 15
DEFAULT_GATHERING(/home/mg/src/deployments/provisioning/ansible.cfg) = smart
DEFAULT_HOST_LIST(/home/mg/src/deployments/provisioning/ansible.cfg) = ['/home/mg/src/deployments/provisioning/inventory']
DEFAULT_LOG_PATH(/home/mg/src/deployments/provisioning/ansible.cfg) = /home/mg/src/deployments/provisioning/.cache/ansible.log
DEFAULT_REMOTE_USER(/home/mg/src/deployments/provisioning/ansible.cfg) = root
DEFAULT_STDOUT_CALLBACK(/home/mg/src/deployments/provisioning/ansible.cfg) = yaml
DEFAULT_VAULT_PASSWORD_FILE(/home/mg/src/deployments/provisioning/ansible.cfg) = /home/mg/src/deployments/provisioning/askpas>
EDITOR(env: EDITOR) = vim
INTERPRETER_PYTHON(/home/mg/src/deployments/provisioning/ansible.cfg) = python3
RETRY_FILES_ENABLED(/home/mg/src/deployments/provisioning/ansible.cfg) = False

CACHE:
=====

jsonfile:
________
_timeout(/home/mg/src/deployments/provisioning/ansible.cfg) = 86400
_uri(/home/mg/src/deployments/provisioning/ansible.cfg) = /home/mg/src/deployments/provisioning/.cache/facts

CONNECTION:
==========

paramiko_ssh:
____________
remote_user(/home/mg/src/deployments/provisioning/ansible.cfg) = root

ssh:
___
remote_user(/home/mg/src/deployments/provisioning/ansible.cfg) = root
```


### OS / Environment

Ubuntu 23.10

### Steps to Reproduce

<!--- Paste example playbooks or commands between quotes below -->
```yaml (paste below)
- hosts: all
  gather_facts: no
  tasks:
    - debug: msg="hello"
      delegate_to: "{{ var }}"
      when: var != ""
      vars:
        var: ""
```


### Expected Results

I expect the task to be skipped.

### Actual Results

```console
$ ansible-playbook -i localhost, ansible-delegate-to-blank.yml -vvvv
ansible-playbook [core 2.16.0]
  config file = None
  configured module search path = ['/home/mg/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/mg/.local/pipx/venvs/ansible/lib/python3.11/site-packages/ansible
  ansible collection location = /home/mg/.ansible/collections:/usr/share/ansible/collections
  executable location = /home/mg/.local/bin/ansible-playbook
  python version = 3.11.6 (main, Oct  8 2023, 05:06:43) [GCC 13.2.0] (/home/mg/.local/pipx/venvs/ansible/bin/python)
  jinja version = 3.1.2
  libyaml = True
No config file found; using defaults
setting up inventory plugins
Loading collection ansible.builtin from 
Set default localhost to localhost
Parsed localhost, inventory source with host_list plugin
Loading callback plugin default of type stdout, v2.0 from /home/mg/.local/pipx/venvs/ansible/lib/python3.11/site-packages/ansible/plugins/callback/default.py
Skipping callback 'default', as we already have a stdout callback.
Skipping callback 'minimal', as we already have a stdout callback.
Skipping callback 'oneline', as we already have a stdout callback.

PLAYBOOK: ansible-delegate-to-blank.yml **************************************************************************************
Positional arguments: ansible-delegate-to-blank.yml
verbosity: 4
connection: ssh
become_method: sudo
tags: ('all',)
inventory: ('localhost,',)
forks: 5
1 plays in ansible-delegate-to-blank.yml

PLAY [all] *******************************************************************************************************************

TASK [debug] *****************************************************************************************************************
task path: /home/mg/tmp/ansible-delegate-to-blank.yml:4
fatal: [localhost -> {{ var }}]: FAILED! => {
    "msg": "Supplied entity must be Host or Group, got <class 'ansible.inventory.host.Host'> instead"
}

PLAY RECAP *******************************************************************************************************************
localhost                  : ok=0    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
return self._extra_vars
    def set_inventory(self, inventory):
        self._inventory = inventory
    def get_vars(self, play=None, host=None, task=None, include_hostvars=True, include_delegate_to=False, use_cache=True,
                 _hosts=None, _hosts_all=None, stage='task'):
        '''
        Returns the variables, with optional "context" given via the parameters
        for the play, host, and task (which could possibly result in different
        sets of variables being returned due to the additional context).
        The order of precedence is:
        - play->roles->get_default_vars (if there is a play context)
        - group_vars_files[host] (if there is a host context)
        - host_vars_files[host] (if there is a host context)
        - host->get_vars (if there is a host context)
        - fact_cache[host] (if there is a host context)
        - play vars (if there is a play context)
        - play vars_files (if there's no host context, ignore
          file names that cannot be templated)
        - task->get_vars (if there is a task context)
        - vars_cache[host] (if there is a host context)
        - extra vars
        ``_hosts`` and ``_hosts_all`` should be considered private args, with only internal trusted callers relying
        on the functionality they provide. These arguments may be removed at a later date without a deprecation