Fix NativeDaemonConnectorException issue accessing null object

When function getCode is called on
NativeDaemonConnectorException object it may throw exception
due to mEvent object not being set for certain constructors.
Fix is to return a default error code as expected if mEvent
object has not been set rather than trying to call
mEvent.getCode().

Change-Id: Ia8aa23deb8871bb4df73096cc489b685a1765f16

services/core/java/com/android/server/NativeDaemonConnectorException.java

@@ -41,7 +41,7 @@ public class NativeDaemonConnectorException extends Exception {
     }
 
     public int getCode() {
-        return mEvent.getCode();
+        return mEvent != null ? mEvent.getCode() : -1;
     }
 
     public String getCmd() {