MDEV-13209 Cross-database operation with virtual columns fails

if we don't need to print field's table name,
we surely don't need to print field's db name either

mysql-test/suite/vcol/r/cross_db.result

@@ -0,0 +1,17 @@
+create database mysqltest1;
+create table mysqltest1.t1 (i int, j int as (i) persistent);
+show create table mysqltest1.t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `i` int(11) DEFAULT NULL,
+  `j` int(11) GENERATED ALWAYS AS (`i`) STORED
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+alter table mysqltest1.t1 add index (i);
+show create table mysqltest1.t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `i` int(11) DEFAULT NULL,
+  `j` int(11) GENERATED ALWAYS AS (`i`) STORED,
+  KEY `i` (`i`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop database mysqltest1;

mysql-test/suite/vcol/t/cross_db.test

@@ -0,0 +1,9 @@
+#
+# MDEV-13209 Cross-database operation with virtual columns fails
+#
+create database mysqltest1;
+create table mysqltest1.t1 (i int, j int as (i) persistent);
+show create table mysqltest1.t1;
+alter table mysqltest1.t1 add index (i);
+show create table mysqltest1.t1;
+drop database mysqltest1;

sql/item.cc

@@ -2669,22 +2669,21 @@ void Item_ident::print(String *str, enum_query_type query_type)
     use_db_name= !(cached_table && cached_table->belong_to_view &&
                    cached_table->belong_to_view->compact_view_format);
 
-  if (!use_db_name && use_table_name &&
-      (query_type & QT_ITEM_IDENT_SKIP_TABLE_NAMES))
+  if (use_table_name && (query_type & QT_ITEM_IDENT_SKIP_TABLE_NAMES))
   {
     /*
       Don't print the table name if it's the only table in the context
       XXX technically, that's a sufficient, but too strong condition
     */
     if (!context)
-      use_table_name= false;
+      use_db_name= use_table_name= false;
     else if (context->outer_context)
       use_table_name= true;
     else if (context->last_name_resolution_table == context->first_name_resolution_table)
-      use_table_name= false;
+      use_db_name= use_table_name= false;
     else if (!context->last_name_resolution_table &&
              !context->first_name_resolution_table->next_name_resolution_table)
-      use_table_name= false;
+      use_db_name= use_table_name= false;
   }
 
   if (!field_name || !field_name[0])