zabbix_action: Fixing the default message checking (#54953)

lib/ansible/modules/monitoring/zabbix/zabbix_action.py

@@ -227,9 +227,11 @@ options:
             message:
                 description:
                     - Operation message text.
+                    - Will check the 'default message' and use the text from I(default_message) if this and I(default_subject) are not specified
             subject:
                 description:
                     - Operation message subject.
+                    - Will check the 'default message' and use the text from I(default_subject) if this and I(default_subject) are not specified
             media_type:
                 description:
                     - Media type that will be used to send the message.
@@ -921,7 +923,7 @@ class Operations(object):
         """
         try:
             return {
-                'default_msg': '0' if 'message' in operation or 'subject' in operation else '1',
+                'default_msg': '0' if operation.get('message') is not None or operation.get('subject')is not None else '1',
                 'mediatypeid': self._zapi_wrapper.get_mediatype_by_mediatype_name(
                     operation.get('media_type')
                 ) if operation.get('media_type') is not None else '0',
@@ -1660,12 +1662,12 @@ def main():
             state=dict(type='str', required=False, default='present', choices=['present', 'absent']),
             status=dict(type='str', required=False, default='enabled', choices=['enabled', 'disabled']),
             pause_in_maintenance=dict(type='bool', required=False, default=True),
-            default_message=dict(type='str', required=False, default=None),
+            default_message=dict(type='str', required=False, default=''),
-            default_subject=dict(type='str', required=False, default=None),
+            default_subject=dict(type='str', required=False, default=''),
-            recovery_default_message=dict(type='str', required=False, default=None),
+            recovery_default_message=dict(type='str', required=False, default=''),
-            recovery_default_subject=dict(type='str', required=False, default=None),
+            recovery_default_subject=dict(type='str', required=False, default=''),
-            acknowledge_default_message=dict(type='str', required=False, default=None),
+            acknowledge_default_message=dict(type='str', required=False, default=''),
-            acknowledge_default_subject=dict(type='str', required=False, default=None),
+            acknowledge_default_subject=dict(type='str', required=False, default=''),
             conditions=dict(
                 type='list',
                 required=False,