empty prefix argument after creating/removing prefix in visual editor

[boyangzhao]

I noticed that the rabix composer can result in an empty prefix '' for an argument if the user in the visual editor 1) first creates an argument with some prefix defined, and 2) remove all the text in the prefix. In the code, the prefix doesn't go away, but instead persists and is defined as prefix: ''. For example, following the above described procedure, you can result in

  - id: input
    type: File?
    inputBinding:
      position: 0
      prefix: ''

This is fine for running on SB platform; but with some cwl executors, this would cause an issue. This would result for example on toil with '' as a literal being used as the prefix for the argument, instead of having no prefix. The happened a few times and took me some time to figure out why I got these weird '' in the commands and had to manually remove those in the cwl code.

Rabix composer version: 1.5.0