Fix crash with C++ qualified names

PR c++/29503 points out that something like "b->Base::member" will
crash when 'b' does not have pointer type.  This seems to be a simple
oversight in eval_op_member.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29503


Reviewed-By: Bruno Larsen <blarsen@redhat.com>