Fill in empty iftable early

Previously it would not get filled in and remain null for some
erroneous classes. This caused crashes for things like
GetIfTableCount.

Added regression test (sample failure):
class_linker_test F 12-15 14:20:09 28771 28771 class-inl.h:532] Check failed: ret != nullptr java.lang.Class<Erroneous>

Bug: 33650297
Bug: 33642884

Test: test-art-host

Change-Id: I506210bad17d6d2c58ca7870165f8a4a514f64fe