ansible-doc - account for empty meta/main.yml (#73590)

* ansible-doc - account for empty meta/main.yml

 from_yaml() will return None when encrounting an empty file.

changelogs/fragments/ansible-doc-role-empty-meta-main.yml

@@ -0,0 +1,4 @@
+bugfixes:
+  - >-
+    ansible-doc - account for an empty ``meta/main.yml`` file when displaying
+    role information (https://github.com/ansible/ansible/pull/73590)

lib/ansible/cli/doc.py

@@ -91,6 +91,8 @@ class RoleMixin(object):
         try:
             with open(path, 'r') as f:
                 data = from_yaml(f.read(), file_name=path)
+                if data is None:
+                    data = {}
                 return data.get('argument_specs', {})
         except (IOError, OSError) as e:
             raise AnsibleParserError("An error occurred while trying to read the file '%s': %s" % (path, to_native(e)), orig_exc=e)