Log.wtf when expanding a goup that's not attached

This seems like it can happen very rarely, though we're not quite sure
how. It's not really an issue since we can just ignore the expansion, so
it shouldn't crash sysui, but made it a Log.wtf so we can still keep an
eye on it.

Bug: 318317068
Test: GroupExpansionManagerTest
Flag: NONE
Change-Id: I16a3f6ced860fee337ccfc8468738ab7cf7b7fca