Need to set ci->proc when we have RProc structure.

Mentioned in https://qiita.com/bamchoh/items/eabebbbb330cb0e0470a

src/vm.c

@@ -475,6 +475,9 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
       int ai = mrb_gc_arena_save(mrb);
 
       ci->acc = CI_ACC_DIRECT;
+      if (MRB_METHOD_PROC_P(m)) {
+        ci->proc = MRB_METHOD_PROC(m);
+      }
       val = MRB_METHOD_CFUNC(m)(mrb, self);
       mrb->c->stack = mrb->c->ci->stackent;
       cipop(mrb);