After I add prev patch to GDB, the GDB got crash when a trace frame didn't include all the variables that it should include.
I think this issue should be handle because the trace frame didn't include all the variables will be always happen (What I use is GDB and gdbserver).
So I post this patch to handle it.

Thanks,
Hui

2012-11-20  Hui Zhu  <hui_zhu@mentor.com>

	* dwarf2loc.c (dwarf_expr_frame_base): Add check for the return
	value of get_frame_block.