vm_call_bmethod should not drop the empty keyword hash

Similar to 38e9c1bc35d5549575fbb263afff560e97db068e

test/ruby/test_keyword.rb

@@ -733,7 +733,9 @@ class TestKeywordArguments < Test::Unit::TestCase
       define_method(:m) {|arg, **opt| [arg, opt] }
     end
     assert_raise(ArgumentError) { c.m(**{}) }
-    assert_raise(ArgumentError) { c.m(**kw) }
+    assert_warn(/The keyword argument is passed as the last hash parameter/m) do
+      assert_equal([kw, kw], c.m(**kw))
+    end
     assert_warn(/The keyword argument is passed as the last hash parameter/m) do
       assert_equal([h, kw], c.m(**h))
     end

vm_insnhelper.c

@@ -2279,7 +2279,7 @@ vm_call_bmethod(rb_execution_context_t *ec, rb_control_frame_t *cfp, struct rb_c
     VALUE *argv;
     int argc;
 
-    CALLER_SETUP_ARG(cfp, calling, ci, 1);
+    CALLER_SETUP_ARG(cfp, calling, ci, 0);
     argc = calling->argc;
     argv = ALLOCA_N(VALUE, argc);
     MEMCPY(argv, cfp->sp - argc, VALUE, argc);