obs-ffmpeg: Check avformat context before use

plugins/obs-ffmpeg/obs-ffmpeg-output.c

@@ -578,6 +578,11 @@ static bool ffmpeg_data_init(struct ffmpeg_data *data,
 	avformat_alloc_output_context2(&data->output, output_format,
 			NULL, NULL);
 
+	if (!data->output) {
+		blog(LOG_WARNING, "Couldn't create avformat context");
+		goto fail;
+	}
+
 	if (is_rtmp) {
 		data->output->oformat->video_codec = AV_CODEC_ID_H264;
 		data->output->oformat->audio_codec = AV_CODEC_ID_AAC;
@@ -586,11 +591,6 @@ static bool ffmpeg_data_init(struct ffmpeg_data *data,
 			set_encoder_ids(data);
 	}
 
-	if (!data->output) {
-		blog(LOG_WARNING, "Couldn't create avformat context");
-		goto fail;
-	}
-
 	if (!init_streams(data))
 		goto fail;
 	if (!open_output_file(data))