[PATCH] Avoid crash with GCC trunk

[Tom Tromey]

>>>>> "Tom" == Tom Tromey <tromey@adacore.com> writes:

Tom> With GCC trunk, gdb.ada/access_to_packed_array.exp causes a GDB crash.
Tom> The problem is that ptype tries to resolve a dynamic type.  However,
Tom> the inferior is not running, so there are no frames.

Tom> This patch updates dwarf2_evaluate_loc_desc::get_frame_base to handle
Tom> this situation.

I'm checking this in.

Tom