libpredict registered the tbc spellcast and combat log events on every
client and relied on vanilla never firing them. A vanilla client with an
API backport such as ClassicAPI fires UNIT_SPELLCAST_START as well, without
UnitCastingInfo, so every cast raised "attempt to call global
'UnitCastingInfo'". Register those events on the tbc client only; vanilla
keeps using its own SPELLCAST events.
some addons like to provide a broken _G variable to
the global environment breaking every other addon that
relies on it if existing. With this commit, make ShaguTweaks
no longer re-use the global _G, even if existing.