Fix GH-16354 convert GMP to number failure.

zend_parse_arg_long_slow/zend_null_arg_deprecated handle nullable
as 2nd (or +) argument so here we trigger a TypeError exception
in case we deal with null at 1st argument.

Author: devnexen

ext/gmp/gmp.c

@@ -619,6 +619,15 @@ static zend_result convert_to_gmp(mpz_t gmpnumber, zval *val, zend_long base, ui
 	case IS_STRING: {
 		return convert_zstr_to_gmp(gmpnumber, Z_STR_P(val), base, arg_pos);
 	}
+	case IS_NULL: {
+		/**
+		 * zend_parse_arg_long_slow support nullable argument but expects it
+		 * to be the 2nd, and onward, argument or non null but at any place.
+		 **/
+		zend_type_error(
+			"Number must be of type GMP|string|int, null given");
+		return FAILURE;
+	}
 	default: {
 		zend_long lval;
 		if (!zend_parse_arg_long_slow(val, &lval, arg_pos)) {