Exit restrictions fragment if user was deleted

When resuming the restricted user fragment, make sure that the user still
exists, as it may have been deleted by the restricted user.

Bug: 11010340

Change-Id: I3360dbc42586c5bb28013844f8c788e641ad8b6a

src/com/android/settings/users/AppRestrictionsFragment.java

@@ -347,6 +347,9 @@ public class AppRestrictionsFragment extends SettingsPreferenceFragment implemen
 
     protected Drawable getCircularUserIcon() {
         Bitmap userIcon = mUserManager.getUserIcon(mUser.getIdentifier());
+        if (userIcon == null) {
+            return null;
+        }
         CircleFramedDrawable circularIcon =
                 CircleFramedDrawable.getInstance(this.getActivity(), userIcon);
         return circularIcon;