apt_repository: check attribute repo for None value (#36944)

lib/ansible/modules/packaging/os/apt_repository.py

@@ -503,6 +503,9 @@ def main():
         else:
             module.fail_json(msg='%s is not installed, and install_python_apt is False' % PYTHON_APT)
 
+    if not repo:
+        module.fail_json(msg='Please set argument \'repo\' to a non-empty value')
+
     if isinstance(distro, aptsources_distro.Distribution):
         sourceslist = UbuntuSourcesList(module, add_ppa_signing_keys_callback=get_add_ppa_signing_key_callback(module))
     else:

test/integration/targets/apt_repository/tasks/apt.yml

@@ -199,6 +199,28 @@
 - name: 'ensure ppa key is absent (expect: pass)'
   apt_key: id='{{test_ppa_key}}' state=absent
 
+- name: Test apt_repository with a null value for repo
+  apt_repository:
+    repo:
+  register: result
+  ignore_errors: yes
+
+- assert:
+    that:
+      - result is failed
+      - result.msg == 'Please set argument \'repo\' to a non-empty value'
+
+- name: Test apt_repository with an empty value for repo
+  apt_repository:
+    repo: ""
+  register: result
+  ignore_errors: yes
+
+- assert:
+    that:
+      - result is failed
+      - result.msg == 'Please set argument \'repo\' to a non-empty value'
+
 #
 # TEARDOWN
 #