Resilience against plugin list exception

[ArneBab]

This is just a band-aid. We may want to copy the plugin list instead.

[Bombe]

Oof, yeah, that’s horrible. getLoadedPlugins() needs to make a copy. Actually, all the getters need to make copies. Who wrote that? (Oh yeah, it was me.)

[ArneBab]

@Bombe I changed the getters to only return copies of the loaded and loading lists. They are only iterated over at all callers. And I found one instance where Toad was being rightfully paranoid about this :-) — now no longer needed.

Is this good to go?

[ArneBab]

merged — thank you for the review!