flex: the fast lexical analyser

yy_top_state crashes when called in state INITIAL!

Version: flex 2.5.35
Machine: SunOS dts06 5.9 Generic_112233-12 sun4u sparc SUNW,Sun-Blade-1500

static int yy_top_state (void)
{
return (yy_start_stack)[(yy_start_stack_ptr) - 1];
}

Code should protect against:
yy_start_stack_ptr = 0 or (yy_start_stack)[ -1 ];