♻️ Make Attachment.save clearer by expliciting that chunksize is non-null

Author: Paillat-dev

discord/message.py

@@ -314,7 +314,7 @@ async def save(
             deleted attachments if too much time has passed, and it does not work
             on some types of attachments.
         chunksize: Optional[:class:`int`]
-            The maximum size of each chunk to process.
+            The maximum size of each chunk to process. Must be a positive non-null integer.
 
         Returns
         -------
@@ -336,7 +336,7 @@ async def save(
             data = await self.read(use_cached=use_cached)
 
         if isinstance(fp, io.BufferedIOBase):
-            if chunksize:
+            if chunksize is not None:
                 written = 0
                 async for chunk in data:
                     written += fp.write(chunk)