Ignore error due to data being received after stream is already closed

[Gruek]

No description provided.

[TomiBelan]

#312 and #334 are exactly equivalent PRs, so I'll comment on both:
The fix LGTM, but I have a small pedantic suggestion. How about get() instead of except KeyError? In theory, it could suppress some other KeyError in nested calls.
(I am a random passerby. This is not some official review. Current version is fine too.)

            elif isinstance(event, h2.events.DataReceived):
                stream = self.streams.get(event.stream_id)
                if not stream:
                    # Data received while already closed, nothing to do.
                    continue
                await stream.handle(Body(stream_id=event.stream_id, data=event.data))
                self.connection.acknowledge_received_data(
                    event.flow_controlled_length, event.stream_id
                )
            elif isinstance(event, h2.events.StreamEnded):
                stream = self.streams.get(event.stream_id)
                if not stream:
                    # Response sent before full request received,
                    # nothing to do already closed.
                    continue
                await stream.handle(EndBody(stream_id=event.stream_id))