DeskClock: Fix DeskClock crash when click dismiss clock

It is the NullPointerException which cause this crash happen

Add a condition to exclude the NullPointerException.

CRs-fixed: 650830

Change-Id: Id45a1ce757dc1876f56bd5d49ba5376760ec4cb8
DeskClock: Fix alarm name display abnormal when choose audio

Lack the handle to uri whose authority is document.

When we judge the uri is from document ,we obtain its name as
title for alarm name.

CRs-fixed: 662043

Change-Id: I588678ee8102adbe661a155e7650f7b50bb5b85e