fix race

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@10535 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/switch_core_io.c

@@ -166,7 +166,7 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_read_frame(switch_core_sessi
 			}
 		}
 		
-		if (!session->read_codec) {
+		if (!SWITCH_READ_ACCEPTABLE(status) || !session->read_codec || !session->read_codec->mutex) {
 			*frame = NULL;
 			return SWITCH_STATUS_FALSE;
 		}