[Bug middle-end/54957] Two crashes introduced by rev192488

[rmansfield at qnx dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54957

--- Comment #9 from Ryan Mansfield <rmansfield at qnx dot com> 2012-10-17 19:05:36 UTC ---
(In reply to comment #8)
> Created attachment 28466 [details]
> Proposed patch
> 
> Handle the possibility that stmt_bb may be NULL in emit_case_dispatch_table.
> Untested.

I was able to reproduce the crash in emit_case_dispatch_table on a stock 
sh4-unknown-linux-gnu configuration with another testcase. This patch fixes the
all crashes I've seen so far.