Merge "Fix b/243746796 Crash when mouse hangs over an empty battery chart"

src/com/android/settings/fuelgauge/batteryusage/BatteryChartView.java

@@ -595,6 +595,7 @@ public class BatteryChartView extends AppCompatImageView implements View.OnClick
 
     // Searches the corresponding trapezoid index from x location.
     private int getTrapezoidIndex(float x) {
+        if (mTrapezoidSlots != null) {
             for (int index = 0; index < mTrapezoidSlots.length; index++) {
                 final TrapezoidSlot slot = mTrapezoidSlots[index];
                 if (x >= slot.mLeft - mTrapezoidHOffset
@@ -602,6 +603,7 @@ public class BatteryChartView extends AppCompatImageView implements View.OnClick
                     return index;
                 }
             }
+        }
         return BatteryChartViewModel.SELECTED_INDEX_INVALID;
     }