Fix padding problem.

library/src/org/whispersystems/textsecure/push/PushTransportDetails.java

@@ -47,7 +47,7 @@ public class PushTransportDetails implements TransportDetails {
       }
     }
 
-    byte[] strippedMessage = new byte[messageWithPadding.length - paddingStart];
+    byte[] strippedMessage = new byte[paddingStart];
     System.arraycopy(messageWithPadding, 0, strippedMessage, 0, strippedMessage.length);
 
     return strippedMessage;