Issue with particular filenames

Thanks for the amazing tool. It has been so easy to use!

While I was converting some of my files, I had one that had a single quote in their name "Winter's Heart". This caused the single quotes used to specify the filename to be prematurely ended and have ffmpeg look for the wrong file. It was simple enough to fix on my end, but adding to check for a single quote in the filename or changing to double quotes could solve the problem.