video not converting ffmpeg clip bucket

Today I have faced an issue while uploading video to clip bucket the video is getting uploaded successfully but the video is not converting.
I have checked the video conversion details from the video manager area and it says Log file was not found

Then I have done some searching and found that the file

includes/classes/conversion/ffmpeg.class.php is causing this issue.

I have commented the following line  and the video converted successfully.

 #$use_vf = config('use_ffmpeg_vf');