yum module handle list optional empty strings properly (#46634)

Fixes #46517

Signed-off-by: Adam Miller <admiller@redhat.com>

lib/ansible/module_utils/yumdnf.py

@@ -130,6 +130,9 @@ class YumDnf(with_metaclass(ABCMeta, object)):
 
         some_list.extend(new_list)
 
+        if some_list == [""]:
+            return []
+
         return some_list
 
     @abstractmethod

test/integration/targets/yum/tasks/yum.yml

@@ -83,6 +83,16 @@
     that:
         - "not yum_result is changed"
 
+- name: install sos again with empty string enablerepo
+  yum: name=sos state=present enablerepo=""
+  register: yum_result
+- name: verify no change on third install with empty string enablerepo
+  assert:
+    that:
+        - "yum_result is success"
+        - "not yum_result is changed"
+
+
 # INSTALL AGAIN WITH LATEST
 - name: install sos again with state latest in check mode
   yum: name=sos state=latest