fix: prevent request handling from processing during abortion

Author: fleming79

ipykernel/kernelbase.py

@@ -439,6 +439,8 @@ async def shell_main(self, subshell_id: str | None):
     async def _execute_request_handler(self, receive_stream):
         async with receive_stream:
             async for handler, (socket, idents, msg) in receive_stream:
+                if self._aborting:
+                    continue
                 try:
                     result = handler(socket, idents, msg)
                     self.set_parent(idents, msg, channel="shell")