ResourceDing

Runs on Classic Era and Season of Discovery.

One line was fatal there. PLAYER_SPECIALIZATION_CHANGED does not exist on a client with no specialisations, and registering an unknown event raises an error — during load, before the addon has done anything. A single absent name did not cost a feature, it took the whole addon down. Every registration is guarded now.

The rest follows from what vanilla actually has:

• Combo points belong to the target there, not to the player, and UnitPower reports none of them. GetComboPoints is what answers, and UNIT_COMBO_POINTS is what fires when they change — no UNIT_POWER event does. Retail is untouched.
• Only the two combo point classes are offered on Classic. Chi, Holy Power, Arcane Charges and the Soul Shard bar were all added by later expansions, and Monk and Evoker do not exist in vanilla. Listing them would have the settings panel announce a resource your class cannot have in that game.
• Sounds the client cannot play are dropped from the list rather than offered as a choice that silently does nothing.

Retail behaviour is unchanged.

Two files: -Classic for Classic Era and Season of Discovery, -Retail for the current game.