Fix NPE crash in UsageAccessDetails

mPackageInfo will be null in RefreshUI method in UsageAccessDetails.java

Bug:https://issuetracker.google.com/issues/65872768


Test:As explained in the link above

Change-Id: I8bd4b822cfe5d8a3347ca7f5886605cbdfb9b8b6
Signed-off-by: tiansiming <tiansiming@xiaomi.com>