Bug#29898: Item_date_typecast::val_int doesn't reset the null_value flag.

The Item_date_typecast::val_int function doesn't reset null_value flag.
This makes all values that follows the first null value to be treated as nulls
and led to a wrong result.

Now the Item_date_typecast::val_int function correctly sets the null_value flag
for both null and non-null values.

mysql-test/r/cast.result

@@ -403,4 +403,15 @@ hex(cast('a' as binary(2)))
 select hex(cast('a' as char(2) binary));
 hex(cast('a' as char(2) binary))
 61
+CREATE TABLE t1 (d1 datetime);
+INSERT INTO t1(d1) VALUES ('2007-07-19 08:30:00'), (NULL),
+('2007-07-19 08:34:00'), (NULL), ('2007-07-19 08:36:00');
+SELECT cast(date(d1) as signed) FROM t1;
+cast(date(d1) as signed)
+20070719
+NULL
+20070719
+NULL
+20070719
+drop table t1;
 End of 5.0 tests

mysql-test/t/cast.test

@@ -237,4 +237,13 @@ select hex(cast('a' as char(2) binary));
 select hex(cast('a' as binary(2)));
 select hex(cast('a' as char(2) binary));
 
+#
+# Bug#29898: Item_date_typecast::val_int doesn't reset the null_value flag.
+#
+CREATE TABLE t1 (d1 datetime);
+INSERT INTO t1(d1) VALUES ('2007-07-19 08:30:00'), (NULL),
+  ('2007-07-19 08:34:00'), (NULL), ('2007-07-19 08:36:00');
+SELECT cast(date(d1) as signed) FROM t1;
+drop table t1;
+
 --echo End of 5.0 tests

sql/item_timefunc.cc

@@ -2662,11 +2662,8 @@ longlong Item_date_typecast::val_int()
 {
   DBUG_ASSERT(fixed == 1);
   MYSQL_TIME ltime;
-  if (args[0]->get_date(&ltime, TIME_FUZZY_DATE))
-  {
-    null_value= 1;
+  if ((null_value= args[0]->get_date(&ltime, TIME_FUZZY_DATE)))
     return 0;
-  }
   return (longlong) (ltime.year * 10000L + ltime.month * 100 + ltime.day);
 }