DataPicker throwing ArrayIndexOutOfBoundsException

This is a fix for the DataPicker which throws the
ArrayIndexOutOfBoundsException if the DatePicker.update() is called from
user code. This issue was reported by Max Shirshin who observed it in
the GTasks application and in the DaysUtil Widget.

Change-Id: I7dbc09a2a208d6c2141540eea93586cb6928ae89