A fix: 'information_schema' test with ps-protocol option fails

table_list->schema_table_name may be 0 in this case and 'strcasecmp' is 
not necessary in this case.

sql/sql_show.cc

@@ -3191,6 +3191,7 @@ int mysql_schema_table(THD *thd, LEX *lex, TABLE_LIST *table_list)
     views
     working correctly
   */
+  if (table_list->schema_table_name)
     table->alias_name_used= my_strcasecmp(table_alias_charset,
                                           table_list->schema_table_name,
                                           table_list->alias);