Fix crash if StmtProfile finds a type-dependent member access for which we have

resolved the -> to a call to a specific operator-> function. The particular
test case added here is actually being mishandled: the implicit member access
should not be type-dependent (because it's accessing a non-type-dependent
member of the current instantiation), but calls to a type-dependent operator->
that is a member of the current instantiation would be liable to hit the same
codepath.

llvm-svn: 284999