ChargingControl: No need to log a crash when not supported

Instead of relying on catching the exception later on, check if
ChargingControl is actually supported before checking if a specific
mode is

Change-Id: Icaf8d333842c9847bea00bedb4b302b7acd49bb3
diff --git a/src/org/omnirom/omnilib/internal/health/ChargingControlController.java b/src/org/omnirom/omnilib/internal/health/ChargingControlController.java
index f3237f2..a278802 100644
--- a/src/org/omnirom/omnilib/internal/health/ChargingControlController.java
+++ b/src/org/omnirom/omnilib/internal/health/ChargingControlController.java
@@ -255,7 +255,7 @@
 
     public boolean isChargingModeSupported(int mode) {
         try {
-            return (mChargingControl.getSupportedMode() & mode) != 0;
+            return isSupported() && (mChargingControl.getSupportedMode() & mode) != 0;
         } catch (RemoteException e) {
             throw new RuntimeException(e);
         }