Avoid SystemUI crash due to NPE

BaseStatusBar.createNotificationViews() returns null
when it reports handleNotificationError(), leading to
a forced crash of the misbehaving app. However, it
should not add a null object of Notification.Entry
since it will also crash SystemUI (crashing at compare).

Change-Id: I6b0c933b76a7e271651a08b5eb0f755077b5cb95
Merge "Avoid SystemUI crash due to NPE" into pac-4.4