http2: call the handle-closed function correctly on closed stream

This was this one condition where the stream could be closed due to an
error and the function would still wrongly just return 0 for it.

Reported-by: Gergely Nagy
Fixes #6862
Closes #6910

lib/http2.c

@@ -1609,6 +1609,10 @@ static ssize_t http2_recv(struct Curl_easy *data, int sockindex,
     return -1;
   }
 
+  if(stream->closed)
+    /* closed overrides paused */
+    return http2_handle_stream_close(conn, data, stream, err);
+
   /* Nullify here because we call nghttp2_session_send() and they
      might refer to the old buffer. */
   stream->upload_mem = NULL;