[IMPR] fix inconsistent return statement

Change-Id: Id267a4f03f6566e833ddf37889b11b793a796306
---
M pywikibot/flow.py
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/pywikibot/flow.py b/pywikibot/flow.py
index ce653ed..a6c9e0c 100644
--- a/pywikibot/flow.py
+++ b/pywikibot/flow.py
@@ -318,7 +318,7 @@
         self.site.restore_topic(self, reason)
         self._reload()
 
-    def summary(self) -> Union[str, None]:
+    def summary(self) -> Optional[str]:
         """Get this topic summary, if any.
 
         :return: summary or None
@@ -326,6 +326,7 @@
         if 'summary' in self.root._current_revision.keys():
             return self.root._current_revision['summary']['revision'][
                 'content']['content']
+        return None
 
     def summarize(self, summary: str) -> None:
         """Summarize this topic.

