It was related to that issue but it was meant to fix this reported issue:
https://www.mobileread.com/forums/sh...d.php?t=368699
That basic regex should have worked to repeatedly find everything on that page line by line, not just the first line.
But frankly Sigil's internal search logic all the way back to Sigil 0.6x timeframe never recorded or worked with empty matches. This change should have been done long ago.
Here is the physical change:
https://github.com/Sigil-Ebook/Sigil...f15b274338bbd7
Why the interest?