Correction for the patch to fix mdev-16473.

sql/sql_base.cc

@@ -3331,7 +3331,7 @@ open_and_process_table(THD *thd, LEX *lex, TABLE_LIST *tables,
     Not a placeholder: must be a base/temporary table or a view. Let us open it.
   */
 
-  if (tables->db == no_db)
+  if (tables->db[0] == no_db[0])
   {
     my_message(ER_NO_DB_ERROR, ER(ER_NO_DB_ERROR), MYF(0));
     error= TRUE;

sql/sql_class.h

@@ -3960,8 +3960,8 @@ class THD :public Statement,
         return TRUE;
       }
       /* This will allow to throw an error later for non-CTE references */
-      *p_db= (char *) no_db;
       *p_db_length= strlen(no_db);
+      *p_db= strmake(no_db, *p_db_length);
     }
     else
     {