Merge pull request #5782 from haramako/crash-on-resume-from-cfunc

Protect when call Fiber#resume from C function.

mrbgems/mruby-fiber/src/fiber.c

@@ -267,6 +267,7 @@ fiber_resume(mrb_state *mrb, mrb_value self)
   mrb_int len;
   mrb_bool vmexec = FALSE;
 
+  fiber_check_cfunc(mrb, mrb->c);
   mrb_get_args(mrb, "*!", &a, &len);
   if (mrb->c->ci->cci > 0) {
     vmexec = TRUE;