[LV] Account IV recipes being uniform in VPTransformState::get().

This patch fixes a crash when trying to get a scalar value using
VPTransformState::get() for uniform induction values or truncated
induction values. IVs and truncated IVs can be uniform and the updated
code accounts for that, fixing the crash.

This should fix
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=31981