coa.2: guard CoA data shapes (custom classes, comm-seeded records, ungeared chars)

Fixes login/UI crashes on Vol'jin - CoA Beta:
- DataStore_Inventory: GetAverageItemLevel returns 0 not nil (Altoholic sort
  + AccountSummary iLvl format); guard login AIL broadcast and 0/0 average.
- DataStore_Pets: GetNumPets returns 0 for unscanned companion table instead
  of assert-crashing TabCharacters.
- DataStore_Characters: GetColoredCharacterName tolerates nil name.
- Altoholic/Characters.lua: GetLineType returns nil for stale line id.

Stamp -coa.2 + X-Edited-By: Exiles on touched addons; README CoA changelog.

DataStore_Characters/DataStore_Characters.toc

@@ -2,7 +2,8 @@
 ## Title: DataStore_Characters
 ## Notes: Stores information about characters (race, level, etc..)
 ## Author: Thaoky (EU-Marécages de Zangar)
-## Version: 3.3.001
+## X-Edited-By: Exiles (Sub-Net)
+## Version: 3.3.001-coa.2
 ## Dependencies: DataStore
 ## OptionalDeps: Ace3
 ## SavedVariables: DataStore_CharactersDB