Return None after final message

lib/xenu_nntp/mbox.py

@@ -72,6 +72,7 @@ class MBoxReader():
             # We have reached the final message in the stream.
             #
             if line is None or line == '':
+                if self.message:
                     ret = self.message
                     ret.finish()
 
@@ -79,6 +80,8 @@ class MBoxReader():
 
                     return ret
 
+                return None
+
             line = line.replace('\x00', '')
 
             self.line += 1