fix: check for unknown/None content_type for pastebin uploader

Author: onerandomusername

bot/exts/utils/attachment_pastebin_uploader.py

@@ -77,8 +77,24 @@ async def on_message_delete(self, message: discord.Message) -> None:
     @commands.Cog.listener()
     async def on_message(self, message: discord.Message) -> None:
         """Listens for messages containing attachments and offers to upload them to the pastebin."""
-        # Check if the message contains an embedded file and is not sent by a bot or in DMs.
-        if message.author.bot or not message.guild or not any("charset" in a.content_type for a in message.attachments):
+        # Check the message is not sent by a bot or in DMs.
+        if message.author.bot or not message.guild:
+            return
+
+        # Check if the message contains any text-based attachments.
+        # Note that Discord does not always provide a content type
+        # its not good enough to check the content type is text/plain,
+        # we still need to check the charset
+        attachments: list[discord.Attachment] = []
+        for attachment in message.attachments:
+            if (
+                attachment.content_type
+                and attachment.content_type.startswith("text/plain")
+                and "charset" in attachment.content_type
+            ):
+                attachments.append(attachment)
+
+        if not attachments:
             return
 
         log.trace(f"Offering to upload attachments for {message.author} in {message.channel}, message {message.id}")
@@ -106,11 +122,7 @@ async def on_message(self, message: discord.Message) -> None:
         self.pending_messages.discard(message.id)
 
         # Extract the attachments.
-        files = [
-            await self._convert_attachment(f)
-            for f in message.attachments
-            if "charset" in f.content_type
-        ]
+        files = [await self._convert_attachment(f) for f in attachments]
 
         # Upload the files to the paste bin, exiting early if there's an error.
         log.trace(f"Attempting to upload {len(files)} file(s) to pastebin.")