mysqladmin did not have enough space allocated for tracking all variables

when using --vertical or --relative with extended-status. (Bug #40395)

  This patch simply increases the buffer size and adds an assert to
  check that it is big enough -- a more comprehensive fix would dynamically
  allocate the appropriate buffers.

client/mysqladmin.cc

@@ -24,7 +24,7 @@
 #include <mysql.h>
 
 #define ADMIN_VERSION "8.42"
-#define MAX_MYSQL_VAR 256
+#define MAX_MYSQL_VAR 512
 #define SHUTDOWN_DEF_TIMEOUT 3600		/* Wait for shutdown */
 #define MAX_TRUNC_LENGTH 3
 
@@ -743,6 +743,9 @@ static int execute_commands(MYSQL *mysql,int argc, char **argv)
 			mysql_error(mysql));
 	return -1;
       }
+
+      DBUG_ASSERT(mysql_num_rows(res) < MAX_MYSQL_VAR);
+
       if (!opt_vertical)
 	print_header(res);
       else