WowAce

UpdateRoster in GridRoster has a loop that clears roster_units[guid], probably removing valid guids.  This one probably explains why res sometimes fails to find the res target.

All right I took one pass at this. UNIT_PET now works correctly (as tested by hopping on and off vehicles). The whole shebang seems to survive an AV and WG with only player left in roster_units. I will monitor it for a bit after raids this week as well.

I am not sure if I went overboard on the checks though and not clear if line 243 should check if UnitGUID(oldUnit) matches up to oldGuid or not.

Should there be a 1-1 correspondence between unit / guid, or can there be multiple units per guid? I am assuming multiple but then again the 3 trees from the chicken spell only show up 1/3 units. Is that a flaw in the blizz unit frames or are we nubbing something?