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

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
 #