Fix: Android commissioning complete crash (#22747)

When the Thread device is set up first, operationalDatasetBytes has been released, but has not been assigned to nullptr.
After setup a non-Thread device, ReleaseByteArrayElements will be called again, and a crash will occur

src/controller/java/AndroidDeviceControllerWrapper.cpp

@@ -439,6 +439,7 @@ void AndroidDeviceControllerWrapper::OnCommissioningComplete(NodeId deviceId, CH
     {
         env->ReleaseByteArrayElements(operationalDatasetBytes, operationalDataset, 0);
         env->DeleteGlobalRef(operationalDatasetBytes);
+        operationalDatasetBytes = nullptr;
     }
 }