gcc 4.0 generates location list without DW_AT_frame_base

[Daniel Berlin]

> 0x000000000055c84d in add_location_or_const_value_attribute
> (die=0x2a96205820,
>    decl=0x2a961ad000, attr=DW_AT_location)
>    at /export/gnu/src/gcc/gcc/gcc/dwarf2out.c:10108
> 10108         descr = loc_descriptor (NOTE_VAR_LOCATION
> (node->var_loc_note),
> (gdb) p *loc_list
> $4 = {first = 0x0, last = 0x0, decl_id = 14047}
> (gdb)

Oh, that's weird.
Wonder why we added it then.
anyway, just change
if (loc_list)
to
if (loc_list && loc_list->first)