[FIX] m.DatePicker unneccessary change event if value was set to null

Change-Id: Ia05d24917be1b37707a6befd7c52efa2617abfb0
BCP: 1482023605
CR-Id: 012003146900009355512014
Merge "[FIX] m.DatePicker unneccessary change event if value was set to null" into rel-1.26