livecheck: Stop on negative regexp offset
livecheck: Stop on negative regexp offset

If the given regex is an empty string, regexp returns indices {0 -1}.
This -1 was taken as the offset where to start applying the regex again,
leading to an infinite loop handling the same line over and over.

neverpanic/macports-base,neverpanic/macports-base,macports/macports-base,danchr/macports-base,danchr/macports-base,macports/macports-base