[Ad Blocker][Crash] Properly report when compiled list validation failed (VB-131982)

This should fix the crash reported by @temp99 with adding a "giant" blocklist:
https://forum.vivaldi.net/post/924110

[Ad Blocker] Check for invalid rule lists before parsing them (VB-132030)

Hopefully this will give better feedback to users trying to add webpages as blocklists and not plain text files as they should.