DEV-7221 from_days fails after null value

mysql-test/r/func_time.result

@@ -2561,3 +2561,27 @@ Warning	1292	Truncated incorrect time value: '9336:00:00'
 Warning	1292	Truncated incorrect time value: '2952:00:00'
 Warning	1292	Truncated incorrect time value: '2952:00:00'
 DROP TABLE t1;
+#
+# MDEV-7221 from_days fails after null value
+#
+CREATE TABLE t1 (
+id INT(11) NOT NULL PRIMARY KEY,
+date1 DATE NULL DEFAULT NULL
+);
+INSERT INTO t1 VALUES (12, '2011-05-12');
+INSERT INTO t1 VALUES (13, NULL);
+INSERT INTO t1 VALUES (14, '2009-10-23');
+INSERT INTO t1 VALUES (15, '2014-10-30');
+INSERT INTO t1 VALUES (16, NULL);
+INSERT INTO t1 VALUES (17, NULL);
+INSERT INTO t1 VALUES (18, '2010-10-13');
+SELECT a.id,a.date1,FROM_DAYS(TO_DAYS(a.date1)-10) as date2, DATE_ADD(a.date1,INTERVAL -10 DAY),TO_DAYS(a.date1)-10 FROM t1 a ORDER BY a.id;
+id	date1	date2	DATE_ADD(a.date1,INTERVAL -10 DAY)	TO_DAYS(a.date1)-10
+12	2011-05-12	2011-05-02	2011-05-02	734624
+13	NULL	NULL	NULL	NULL
+14	2009-10-23	2009-10-13	2009-10-13	734058
+15	2014-10-30	2014-10-20	2014-10-20	735891
+16	NULL	NULL	NULL	NULL
+17	NULL	NULL	NULL	NULL
+18	2010-10-13	2010-10-03	2010-10-03	734413
+DROP TABLE t1;

mysql-test/t/func_time.test

@@ -1561,3 +1561,21 @@ CREATE TABLE t1 ( d DATE, t TIME );
 INSERT INTO t1 VALUES ('2008-12-05','22:34:09'),('2005-03-27','14:26:02');
 SELECT EXTRACT(DAY_MINUTE FROM GREATEST(t,d)), GREATEST(t,d) FROM t1;
 DROP TABLE t1;
+
+
+--echo #
+--echo # MDEV-7221 from_days fails after null value
+--echo #
+CREATE TABLE t1 (
+ id INT(11) NOT NULL PRIMARY KEY,
+ date1 DATE NULL DEFAULT NULL
+);
+INSERT INTO t1 VALUES (12, '2011-05-12');
+INSERT INTO t1 VALUES (13, NULL);
+INSERT INTO t1 VALUES (14, '2009-10-23');
+INSERT INTO t1 VALUES (15, '2014-10-30');
+INSERT INTO t1 VALUES (16, NULL);
+INSERT INTO t1 VALUES (17, NULL);
+INSERT INTO t1 VALUES (18, '2010-10-13');
+SELECT a.id,a.date1,FROM_DAYS(TO_DAYS(a.date1)-10) as date2, DATE_ADD(a.date1,INTERVAL -10 DAY),TO_DAYS(a.date1)-10 FROM t1 a ORDER BY a.id;
+DROP TABLE t1;

sql/item_timefunc.cc

@@ -1488,10 +1488,9 @@ String *Item_temporal_func::val_str(String *str)
 bool Item_func_from_days::get_date(MYSQL_TIME *ltime, ulonglong fuzzy_date)
 {
   longlong value=args[0]->val_int();
-  if (args[0]->null_value)
-    return (null_value= 1);
-  if ((fuzzy_date & TIME_NO_ZERO_DATE) && value == 0)
-    return (null_value= 1);
+  if ((null_value= (args[0]->null_value ||
+                    ((fuzzy_date & TIME_NO_ZERO_DATE) && value == 0))))
+    return true;
   bzero(ltime, sizeof(MYSQL_TIME));
   if (get_date_from_daynr((long) value, &ltime->year, &ltime->month,
                           &ltime->day))