Don't show low battery tip when estimation is zero

It means invalid when estimation is zero. We should catch this case
int LowBatteryDetector and don't show it.

Change-Id: I01dd50616f54162a6688257f4bdb329dfa351bc5
Fixes: 110226028
Test: RunSettingsRoboTests

src/com/android/settings/fuelgauge/batterytip/detectors/LowBatteryDetector.java

@@ -47,7 +47,7 @@ public class LowBatteryDetector implements BatteryTipDetector {
     public BatteryTip detect() {
         final boolean powerSaveModeOn = mPowerManager.isPowerSaveMode();
         final boolean lowBattery = mBatteryInfo.batteryLevel <= mWarningLevel
-                || (mBatteryInfo.discharging
+                || (mBatteryInfo.discharging && mBatteryInfo.remainingTimeUs != 0
                 && mBatteryInfo.remainingTimeUs < TimeUnit.HOURS.toMicros(mPolicy.lowBatteryHour));
 
         int state = BatteryTip.StateType.INVISIBLE;