fix(autogist): empty files should not be uploaded

Author: Jackenmen

autogist/autogist.py

@@ -601,7 +601,8 @@ async def on_message(self, message: discord.Message) -> None:
         author = message.author
 
         filename, content = await fetch_attachment_from_message(message)
-        if content is None:
+        if not content:
+            # content could not be decoded (is None) *or* the file is empty (== "")
             return
 
         try: