access to deleted pointer in flow.c

[Roman Zippel]

Hi,

Since the weekend I have random failures during bootstrap, it's not
crashing everytime but it always fails with same pattern. I tried
electric-fence and found one access to an already deleted pointer in
try_simplify_condjump. After the call to redirect_edge_succ_nodup
cbranch_jump_edge/cbranch_fallthru_edge might be removed (in my case it
was cbranch_fallthru_edge).

bye, Roman