Add NullPtrCheck when smearing in settings

This only happens in new device with broken power_profile.xml, in
which it doesn't have screen power model.

This CL catches the null pointer crash and log it.

Change-Id: Iac23e3a8fc51385bdb22979c4b59000319f6fd49
Fixes: 74617269
Test: RunSettingsRoboTests

src/com/android/settings/fuelgauge/BatteryUtils.java

@@ -214,6 +214,11 @@ public class BatteryUtils {
         }
 
         if (totalActivityTimeMs >= 10 * DateUtils.MINUTE_IN_MILLIS) {
+            if (screenSipper == null) {
+                Log.e(TAG, "screen sipper is null even when app screen time is not zero");
+                return;
+            }
+
             final double screenPowerMah = screenSipper.totalPowerMah;
             for (int i = 0, size = sippers.size(); i < size; i++) {
                 final BatterySipper sipper = sippers.get(i);