FS-7656 fix various edge cases with video and non video files mixed into a source, fix a typo bug in file_read_video and fix same bug in mod_vlc, add a new flag to file_read_video to check if the handle is has active video, make mod_conference move the video in and out of a layer when the stream has video or not

src/mod/applications/mod_av/avformat.c

@@ -1578,6 +1578,10 @@ static switch_status_t av_file_read(switch_file_handle_t *handle, void *data, si
 	av_file_context_t *context = (av_file_context_t *)handle->private_info;
 	int size;
 
+	if ((flags & SVR_CHECK)) {
+		return SWITCH_STATUS_BREAK;
+	}
+
 	if (!context->has_audio && context->has_video && switch_queue_size(context->eh.video_queue) > 0) {
 		memset(data, 0, *len * handle->channels * 2);
 		return SWITCH_STATUS_SUCCESS;