Make sure var beginning is always defined

To prevent unbound Errors caused by using undeclared variable beginning
if the redfam-section does not contain any timestamp

Related Task: [https://fs.golderweb.de/index.php?do=details&task_id=76 FS#76]

redfam.py

@@ -401,6 +401,10 @@ class RedFamParser( RedFam ):
 
             else:
                 ending = None
+        # Missing dates (Task: FS#76)
+        else:
+            beginning = None
+            ending = None
 
         return (beginning, ending)