How to remove comma from combined fields which should be null?

[المشرف العام]

I have Drivers License as one field and State as the other and there are to be combined and formatted as Drivers License, State. How do I handle records that do not have either a Drivers License or State so that the field does not have a comma populated in it

Example:

Record One: XXXXXX, ST

Record Two: ,

Record Three: XXXXX, ST

Record Four: ,

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