Need help with regex in 'tag' menu

[khedger]

I have a simple problem that I hope you have an answer for.
I have a bunch of tags loaded into spreadsheet view. I have several tags for the same album, which are currently blank. I highlight the tags in question and got to regex replace->album. In the submenu I've tried a bunch of different things to detect the empty strings ' ', " ", "NULL", \s, etc. and nothing seems to detect the empty strings in the selected tags. How do I express a regex for a blank line that I want to replace in a tag?

Thanks.