Improve Zephir constant get

[chrysanthemum]

test/flow/switchflow.zep

    public function testSwitch14(result_type = 1)
    {
        var ret;

        switch (result_type) {
            case 1:
            case MYSQL_ASSOC:
            case MYSQLI_ASSOC:
                let ret = "aaa";      <----- cannot execute
                break;

            default:
                let ret = "bbb";      <----- cannot execute
                break;
        }

        return ret;
    }

ext/test/flow/switchflow.zep.c

PHP_METHOD(Test_Flow_SwitchFlow, testSwitch14) {

	zephir_method_globals *ZEPHIR_METHOD_GLOBALS_PTR = NULL;
	zval *result_type = NULL, result_type_sub, ret, _0;
	zval *this_ptr = getThis();

	ZVAL_UNDEF(&result_type_sub);
	ZVAL_UNDEF(&ret);
	ZVAL_UNDEF(&_0);

	ZEPHIR_MM_GROW();
	zephir_fetch_params(1, 0, 1, &result_type);

	if (!result_type) {
		result_type = &result_type_sub;
		ZEPHIR_INIT_VAR(result_type);
		ZVAL_LONG(result_type, 1);
	}


	do {
		ZEPHIR_INIT_VAR(&_0);
		ZEPHIR_MM_GET_CONSTANT(&_0, "MYSQL_ASSOC");
		if (ZEPHIR_IS_LONG(result_type, 1) || ZEPHIR_IS_LONG(result_type, 1) || ZEPHIR_IS_EQUAL(result_type, &_0)) {
			ZEPHIR_INIT_VAR(&ret);
			ZVAL_LONG(&ret, 2);
			break;
		}
		ZEPHIR_INIT_NVAR(&ret);
		ZVAL_LONG(&ret, 4);
		break;
	} while(0);

	RETURN_CCTOR(&ret);

}

kernel/main.h

#define ZEPHIR_MM_GET_CONSTANT(return_value, const_name) do { \
	zval *_constant_ptr = zend_get_constant_str(SL(const_name)); \
	if (_constant_ptr == NULL) { \
		ZEPHIR_MM_RESTORE(); \         <----------------------------
		return; \                      <----------------------------
	} \
	ZVAL_COPY(return_value, _constant_ptr); \
} while(0)

To such

#define ZEPHIR_MM_GET_CONSTANT(return_value, const_name) do { \
	zval *_constant_ptr = zend_get_constant_str(SL(const_name)); \
	if (_constant_ptr == NULL) { \
		ZVAL_NULL(_constant_ptr); \      <---------------------------
	} \
	ZVAL_COPY(return_value, _constant_ptr); \
} while(0)

question:

The constant MYSQL_ASSOC is not in php7, or cannot find a constant.
Thus, the following code cannot execute because of the ZEPHIR_MM_GET_CONSTANT macro.
In the switch syntax also do constant detection.
I'd like to ask: Does it make sense to delete the direct return code of the ZEPHIR_MM_GET_CONSTANT macro?

Thank you very much!

@sergeyklay @dreamsxin