MDEV-27860 SIGSEGV in spider_parse_connect_info on CREATE TABLE

Check if option_struct is NULL in spider_parse_connect_info().

storage/spider/mysql-test/spider/feature/r/engine_defined_attributes.result

@@ -216,6 +216,12 @@ PARTITION BY HASH (a) PARTITIONS 2;
 SELECT * FROM tbl_a;
 ERROR HY000: Unable to connect to foreign data source: localhost
 DROP TABLE tbl_a;
+# MDEV-27860 SIGSEGV in spider_parse_connect_info on CREATE TABLE
+CREATE TABLE tbl_a ENGINE=SPIDER COMMENT="TABLE 'unknown_table'"
+PARTITION BY LIST COLUMNS (c) (
+PARTITION p DEFAULT COMMENT="srv 'unknown_server'" ENGINE=SPIDER
+);
+ERROR HY000: The foreign server name you are trying to reference does not exist. Data source error:  unknown_server
 connection child2_1;
 DROP DATABASE auto_test_remote;
 connection child2_2;

storage/spider/mysql-test/spider/feature/t/engine_defined_attributes.test

@@ -202,6 +202,13 @@ PARTITION BY HASH (a) PARTITIONS 2;
 SELECT * FROM tbl_a;
 DROP TABLE tbl_a;
 
+--echo # MDEV-27860 SIGSEGV in spider_parse_connect_info on CREATE TABLE
+--error ER_FOREIGN_SERVER_DOESNT_EXIST
+CREATE TABLE tbl_a ENGINE=SPIDER COMMENT="TABLE 'unknown_table'"
+PARTITION BY LIST COLUMNS (c) (
+  PARTITION p DEFAULT COMMENT="srv 'unknown_server'" ENGINE=SPIDER
+);
+
 --connection child2_1
 DROP DATABASE auto_test_remote;
 

storage/spider/spd_table.cc

@@ -2394,7 +2394,8 @@ int spider_parse_connect_info(
           SPIDER_PARAM_LONGLONG("srd", second_read, 0);
           SPIDER_PARAM_DOUBLE("srt", scan_rate, 0);
           SPIDER_PARAM_STR_LIST_CHECK("srv", server_names,
-                                      option_struct->remote_server);
+                                      option_struct &&
+                                          option_struct->remote_server);
           SPIDER_PARAM_DOUBLE("ssr", semi_split_read, 0);
           SPIDER_PARAM_LONGLONG("ssl", semi_split_read_limit, 0);
 #ifdef WITH_PARTITION_STORAGE_ENGINE
@@ -2405,7 +2406,8 @@ int spider_parse_connect_info(
           SPIDER_PARAM_LONGLONG("srs", static_records_for_status, 0);
           SPIDER_PARAM_LONG_LIST_WITH_MAX("svc", tgt_ssl_vscs, 0, 1);
           SPIDER_PARAM_STR_LIST_CHECK("tbl", tgt_table_names,
-                                      option_struct->remote_table);
+                                      option_struct &&
+                                          option_struct->remote_table);
           SPIDER_PARAM_INT_WITH_MAX("tcm", table_count_mode, 0, 3);
           SPIDER_PARAM_LONG_LIST_WITH_MAX("uhd", use_handlers, 0, 3);
           SPIDER_PARAM_INT_WITH_MAX("upu", use_pushdown_udf, 0, 1);
@@ -2420,13 +2422,15 @@ int spider_parse_connect_info(
           goto error;
         case 5:
           SPIDER_PARAM_STR_LIST_CHECK("table", tgt_table_names,
-                                      option_struct->remote_table);
+                                      option_struct &&
+                                          option_struct->remote_table);
           error_num = connect_string_parse.print_param_error();
           goto error;
         case 6:
           SPIDER_PARAM_STR_LIST("driver", tgt_drivers);
           SPIDER_PARAM_STR_LIST_CHECK("server", server_names,
-                                      option_struct->remote_server);
+                                      option_struct &&
+                                          option_struct->remote_server);
           SPIDER_PARAM_STR_LIST("socket", tgt_sockets);
           SPIDER_PARAM_HINT("idx", key_hint, 3, (int) table_share->keys,
             spider_db_append_key_hint);
@@ -2444,7 +2448,8 @@ int spider_parse_connect_info(
           goto error;
         case 8:
           SPIDER_PARAM_STR_LIST_CHECK("database", tgt_dbs,
-                                      option_struct->remote_database);
+                                      option_struct &&
+                                          option_struct->remote_database);
           SPIDER_PARAM_STR_LIST("password", tgt_passwords);
           SPIDER_PARAM_INT_WITH_MAX("sts_mode", sts_mode, 1, 2);
 #ifdef WITH_PARTITION_STORAGE_ENGINE