Typing "target sim" in GDB built with --target=cris-elf, crashes immediately
after being launched with "gdb ./a.out".  The issue is that STATE_PROG_ARGV
may return NULL, and this isn't tested before dereferencing the pointer.

If approved, please could someone commit this for me.
Thanks in advance.

2026-08-01  Roger Sayle  <roger@nextmovesoftware.com>

ChangeLog
	* sim/cris/sim-if.c (sim_open): Check that prog_argv isn't NULL.