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.lua

@@ -169,7 +169,7 @@ do
 end
 
 local function _GetColoredCharacterName(character)
-	return (ClassColors[character.englishClass] or WHITE) .. character.name
+	return (ClassColors[character.englishClass] or WHITE) .. (character.name or "?")		-- CoA: records seeded from guild comm before a full scan have no name yet
 end
 
 local function _GetClassColor(character)