FS-9355: fix segfault in case of null frame

src/switch_core_media.c

@@ -11697,7 +11697,7 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_read_video_frame(switch_core
 		}
 	}
 
-	if ((*frame)->codec) {
+	if ((*frame) && (*frame)->codec) {
 		if (patchers) {
 			switch_set_flag((*frame)->codec, SWITCH_CODEC_FLAG_VIDEO_PATCHING);
 		} else {