I took yours and made a couple of adjustments..
I forgot that this specific field, even when blank, still contains quotation marks at both ends, the first char and last char.. I adjusted the regex in this way.

$2 ~ /^["][ ]+["]$/

1. First and last char must be a quotation.
2. One or more spaces much match in between.

This tells me if a field is blank/has no value (assuming there will always be quotes at either end).

Ah, I posted after you did, your regex looks better than mine.
Thanks. I like the * idea better since, perhaps, there may come a time when there will be no spaces in between the quotes.