MDEV-29011 Server crash in spider_db_open_item_cond with XOR operator

Item_func_xor and Item_cond are both derived class of Item_bool_func.
Spider converts *Item_func_xor to *Item_cond and then calls the member
function argument_list(), which Item_func_xor does not implement.

storage/spider/mysql-test/spider/bugfix/r/mdev_29011.result

+#
+# MDEV-29011 Server crash in spider_db_open_item_cond with XOR operator
+#
+for master_1
+for child2
+child2_1
+child2_2
+child2_3
+for child3
+connection child2_1;
+CREATE DATABASE auto_test_remote;
+USE auto_test_remote;
+CREATE TABLE tbl_a (
+a INT,
+b INT
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+INSERT INTO tbl_a VALUES (0, 0), (0, 1), (1, 0), (1, 1);
+connection master_1;
+CREATE DATABASE auto_test_local;
+USE auto_test_local;
+CREATE TABLE tbl_a (
+a INT,
+b INT
+) ENGINE=Spider DEFAULT CHARSET=utf8 COMMENT='table "tbl_a", srv "s_2_1"';
+SELECT a XOR b AS f FROM tbl_a;
+f
+0
+1
+1
+0
+connection master_1;
+DROP DATABASE IF EXISTS auto_test_local;
+connection child2_1;
+DROP DATABASE IF EXISTS auto_test_remote;
+for master_1
+for child2
+child2_1
+child2_2
+child2_3
+for child3

storage/spider/mysql-test/spider/bugfix/t/mdev_29011.cnf

+!include include/default_mysqld.cnf
+!include ../my_1_1.cnf
+!include ../my_2_1.cnf

storage/spider/mysql-test/spider/bugfix/t/mdev_29011.test

+--echo #
+--echo # MDEV-29011 Server crash in spider_db_open_item_cond with XOR operator
+--echo #
+
+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+--connection child2_1
+CREATE DATABASE auto_test_remote;
+USE auto_test_remote;
+eval CREATE TABLE tbl_a (
+    a INT,
+    b INT
+) $CHILD2_1_ENGINE $CHILD2_1_CHARSET;
+INSERT INTO tbl_a VALUES (0, 0), (0, 1), (1, 0), (1, 1);
+
+--connection master_1
+CREATE DATABASE auto_test_local;
+USE auto_test_local;
+eval CREATE TABLE tbl_a (
+    a INT,
+    b INT
+) $MASTER_1_ENGINE $MASTER_1_CHARSET COMMENT='table "tbl_a", srv "s_2_1"';
+
+SELECT a XOR b AS f FROM tbl_a;
+
+--connection master_1
+DROP DATABASE IF EXISTS auto_test_local;
+
+--connection child2_1
+DROP DATABASE IF EXISTS auto_test_remote;
+
+--disable_query_log
+--disable_result_log
+--source ../t/test_deinit.inc
+--enable_query_log
+--enable_result_log

storage/spider/spd_db_mysql.cc

@@ -5002,16 +5002,6 @@ int spider_db_mbase_util::open_item_func(
       last_str = SPIDER_SQL_CLOSE_PAREN_STR;
       last_str_length = SPIDER_SQL_CLOSE_PAREN_LEN;
       break;
-#ifdef MARIADB_BASE_VERSION
-    case Item_func::XOR_FUNC:
-#else
-    case Item_func::COND_XOR_FUNC:
-#endif
-      if (str)
-        str->length(str->length() - SPIDER_SQL_OPEN_PAREN_LEN);
-      DBUG_RETURN(
-        spider_db_open_item_cond((Item_cond *) item_func, spider, str,
-          alias, alias_length, dbton_id, use_fields, fields));
     case Item_func::TRIG_COND_FUNC:
       DBUG_RETURN(ER_SPIDER_COND_SKIP_NUM);
     case Item_func::GUSERVAR_FUNC:
@@ -5095,6 +5085,7 @@ int spider_db_mbase_util::open_item_func(
     case Item_func::LE_FUNC:
     case Item_func::GE_FUNC:
     case Item_func::GT_FUNC:
+    case Item_func::XOR_FUNC:
       if (str)
       {
         func_name = (char*) item_func->func_name();