WOH editor fails when input has uneven width or height

Steps to reproduce:
1. Upload a video file with uneven width or height
2. Use the workflow "Process upon upload and schedule" and select "Hold" on the page "Processing"
3. After having created the event, open the video editor, cut some scenes and try to actually process the video

Actual Results:
Processing the video will fail (WOH editor) since x264 cannot deal with uneven widths and heights. While this is no big deal in encoding profiles (using a scale filter helps), a scale filter cannot be set in this case because WOH editor generates a ffmpeg command already using filters.

Expected Results:
Processing should work

Workaround (if any):