MAINT-2518 : Viewer LLViewerTextureList::removeImageFromList() shouldn't crash Reviewed by Kelly.
MAINT-2518 : Viewer LLViewerTextureList::removeImageFromList() shouldn't crash
Reviewed by Kelly.

gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm,gabeharms/firestorm