Fix crash in Monkey test.

When battery page is launched, BatteryTipLoader will start running.
If we rotate the screen before loader is finished, it will store null
to Bundle and will crash when restoring from that Bundle.

In this cl, we add null pointer check for tip list to avoid the crash.

Also remove a TODO since it is obsolete.

Change-Id: Ic59bc20c633f3a7467f7b5e95da062160bcb4e93
Fixes: 77534165
Test: RunSettingsRoboTests