Adjust row checks.

The one in the paste insertion is to get the insertion index right. The
other two checks are to avoid out-of-bounds errors.
Add a check to see if we're in the middle of an update.

This is to get around a call to reloadData when the rules array changes.
In other words, just circumventing a bit of the observation code.
Fix incorrect flags being used when converting flags to strings.
Filter out empty strings from the selectors array when init'ing with a plist.

They sort of sneak in since the scope string is always defined.