Since Ansible 2.9.8, if the fileglob plugin is passed a path containing
a subdirectory of a non-existent directory, it will fail. For example:
lookup('fileglob', '/'): ok
lookup('fileglob', '/foo'): (non-existent): ok
lookup('fileglob', '/foo/bar'): (non-existent): FAIL
The exact error depends on Python 2 or 3, but here is the error on
Python 2:
AttributeError: 'NoneType' object has no attribute 'endswith'
And on Python 3:
TypeError: expected str, bytes or os.PathLike object, not NoneType
This change fixes the issue by skipping paths that are falsey before
passing them to os.path.join().
Fixes: #69450
