Fix for bug #22824: strict, datetime, NULL, wrong warning

During optimization we replace NULL with 0 for not null 
date{time} fields, so uset MODE_NO_ZERO_DATE flag for a while 
as we don't want to give extra warnings.

mysql-test/r/strict.result

@@ -1352,3 +1352,10 @@ t1	CREATE TABLE `t1` (
   `i` int(11) default NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1 COMMENT='123456789*123456789*123456789*123456789*123456789*123456789*'
 drop table t1;
+set @@sql_mode='NO_ZERO_DATE';
+create table t1(a datetime not null);
+select count(*) from t1 where a is null;
+count(*)
+0
+drop table t1;
+End of 5.0 tests

mysql-test/t/strict.test

@@ -1208,3 +1208,14 @@ create table t1 (i int)
 comment '123456789*123456789*123456789*123456789*123456789*123456789*';
 show create table t1;
 drop table t1;
+
+#
+# Bug #22824: strict, datetime, NULL, wrong warning
+#
+
+set @@sql_mode='NO_ZERO_DATE';
+create table t1(a datetime not null);
+select count(*) from t1 where a is null;
+drop table t1;
+
+--echo End of 5.0 tests

sql/item_cmpfunc.cc

@@ -241,7 +241,8 @@ static bool convert_constant_item(THD *thd, Field *field, Item **item)
   {
     /* For comparison purposes allow invalid dates like 2000-01-32 */
     ulong orig_sql_mode= thd->variables.sql_mode;
-    thd->variables.sql_mode|= MODE_INVALID_DATES;
+    thd->variables.sql_mode= (orig_sql_mode & ~MODE_NO_ZERO_DATE) | 
+                             MODE_INVALID_DATES;
     if (!(*item)->save_in_field(field, 1) && !((*item)->null_value))
     {
       Item *tmp=new Item_int_with_ref(field->val_int(), *item,