##### SUMMARY
<!--- Explain the problem briefly below -->
with_first_found fails "No file was found when using first_found. ..." even if a file matches search conditions, when an undefined variable is used in files parameter.
This is started after I've upgraded from ansible 2.8 to 2.9, so I suppose it is a bug.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
first_found

##### ANSIBLE VERSION
```paste below
ansible 2.9.10
  config file = None
  configured module search path = ['/Users/afunix/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/Cellar/ansible/2.9.10/libexec/lib/python3.8/site-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.8.4 (default, Jul 14 2020, 02:58:48) [Clang 11.0.3 (clang-1103.0.32.62)]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
DEFAULT_VAULT_PASSWORD_FILE(env: ANSIBLE_VAULT_PASSWORD_FILE) = /Users/afunix/.vault
```

##### OS / ENVIRONMENT
Host: macOS 10.15.5
Target: CentOS 7.8


##### STEPS TO REPRODUCE

playbook.yml
```yaml
---
- hosts: all
  roles:
      - test

```

roles/test/tasks/main.yml
```yaml
---
- debug:
      msg: "path: {{role_path}}/vars"

- debug:
    msg: "file: {{ansible_distribution}}-{{ansible_distribution_major_version}}.yml"

- name: Load variables specific for OS family
  include_vars: "{{item}}"
  with_first_found:
    - files:
        - "{{ansible_lsb.id}}-{{ansible_lsb.major_release}}.yml"
        - "{{ansible_distribution}}-{{ansible_distribution_major_version}}.yml"
      paths:
        - "{{role_path}}/vars"

```


roles/test/vars/CentOS-7.yml
```yaml
---
test: test
```


##### EXPECTED RESULTS
ansible-playbook is able to find CentOS-7.yml when running against CentOS 7.8 system, since the file exists.


##### ACTUAL RESULTS
ansible-playbook cannot find CentOS-7.yml when running against CentOS 7.8 system.

The issue goes away once I remove "{{ansible_lsb.id}}-{{ansible_lsb.major_release}}.yml" from files.

Checked ansible -m setup for the host and ansible_lsb is empty.

```paste below
$ ansible-playbook -i inventory playbook.yml 

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

TASK [Gathering Facts] *****************************************************************************************************************************************************************************************
ok: [alice]

TASK [test : debug] ********************************************************************************************************************************************************************************************
ok: [alice] => {
    "msg": "path: /Users/afunix/tmp/ansible-with-first-found/roles/test/vars"
}

TASK [test : debug] ********************************************************************************************************************************************************************************************
ok: [alice] => {
    "msg": "file: CentOS-7.yml"
}

TASK [test : Load variables specific for OS family] ************************************************************************************************************************************************************
fatal: [alice]: FAILED! => {"msg": "No file was found when using first_found. Use errors='ignore' to allow this task to be skipped if no files are found"}

PLAY RECAP *****************************************************************************************************************************************************************************************************
alice                      : ok=3    changed=0    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0   

$ stat /Users/afunix/tmp/ansible-with-first-found/roles/test/vars/CentOS-7.yml
16777220 38020305 -rw-r--r-- 1 afunix staff 0 15 "Jul 20 18:11:55 2020" "Jul 20 18:11:38 2020" "Jul 20 18:11:38 2020" "Jul 20 18:11:38 2020" 4096 8 0 /Users/afunix/tmp/ansible-with-first-found/roles/test/vars/CentOS-7.yml

$ ansible -i inventories/production/hosts -m setup alice | grep ansible_lsb
        "ansible_lsb": {},
```

results = []
        for item_index, item in enumerate(items):
            task_vars['ansible_loop_var'] = loop_var
            task_vars[loop_var] = item
            if index_var:
                task_vars['ansible_index_var'] = index_var
                task_vars[index_var] = item_index
            if extended:
                task_vars['ansible_loop'] = {
                    'index': item_index + 1,
                    'index0': item_index,
                    'first': item_index == 0,
                    'last': item_index + 1 == items_len,
                    'length': items_len,
                    'revindex': items_len - item_index,
                    'revindex0': items_len - item_index - 1,
                }
                if extended_allitems:
                    task_vars['ansible_loop']['allitems'] = items
                try:
                    task_vars['ansible_loop']['nextitem'] = items[item_index + 1]
                except IndexError:
                    pass
                if item_index - 1 >= 0:
                    task_vars['ansible_loop']['previtem'] = items[item_index - 1]
            
            templar.available_variables = task_vars
            
            if loop_pause and ran_once:
                time.sleep(loop_pause)