Bug#48294 assertion when creating a view based on some row() construct in select query

In case of 'CREATE VIEW' subselect transformation does not happen(see JOIN::prepare).
During fix_fields Item_row may call is_null() method for its arugmens which
leads to item calculation(wrong subselect in our case as
transformation did not happen before). This is_null() call
does not make sence for 'CREATE VIEW'.
Note:
Only Item_row is affected because other items don't call is_null() 
during fix_fields() for arguments.

mysql-test/r/view.result:
  test case
mysql-test/t/view.test:
  test case
sql/item_row.cc:
  skip is_null() call in case of 'CREATE VIEW' as unnecessary.

mysql-test/r/view.result

@@ -3868,6 +3868,12 @@ Note	1599	View `test`.`v2` has no creation context
 DROP VIEW v1,v2;
 DROP TABLE t1,t2;
 DROP FUNCTION f1;
+CREATE TABLE t1(f1 INT);
+INSERT INTO t1 VALUES ();
+CREATE VIEW v1 AS SELECT 1 FROM t1 WHERE
+ROW(1,1) >= ROW(1, (SELECT 1 FROM t1 WHERE  f1 >= ANY ( SELECT '1' )));
+DROP VIEW v1;
+DROP TABLE t1;
 # -----------------------------------------------------------------
 # -- End of 5.1 tests.
 # -----------------------------------------------------------------

mysql-test/t/view.test

@@ -3903,6 +3903,19 @@ DROP VIEW v1,v2;
 DROP TABLE t1,t2;
 DROP FUNCTION f1;
 
+
+#
+# Bug#48294 assertion when creating a view based on some row() construct in select query
+#
+CREATE TABLE t1(f1 INT);
+INSERT INTO t1 VALUES ();
+
+CREATE VIEW v1 AS SELECT 1 FROM t1 WHERE
+ROW(1,1) >= ROW(1, (SELECT 1 FROM t1 WHERE  f1 >= ANY ( SELECT '1' )));
+
+DROP VIEW v1;
+DROP TABLE t1;
+
 --echo # -----------------------------------------------------------------
 --echo # -- End of 5.1 tests.
 --echo # -----------------------------------------------------------------

sql/item_row.cc

@@ -71,7 +71,12 @@ bool Item_row::fix_fields(THD *thd, Item **ref)
     Item *item= *arg;
     used_tables_cache |= item->used_tables();
     const_item_cache&= item->const_item() && !with_null;
-    if (const_item_cache)
+    /*
+      Some subqueries transformations aren't done in the view_prepare_mode thus
+      is_null() will fail. So we skip is_null() calculation for CREATE VIEW as
+      not necessary.
+    */
+    if (const_item_cache && !thd->lex->view_prepare_mode)
     {
       if (item->cols() > 1)
 	with_null|= item->null_inside();