message: Initialize fields to nullptr to avoid crashes
  This happens when a Texture with no callback is created.
diff: struct CallbackJni {
  #ifdef ANDROID
  - jclass handlerClass;
  - jmethodID post;
  + jclass handlerClass = nullptr;
  + jmethodID post = nullptr;
  #endif
  - jclass executorClass;
  - jmethodID execute;
  + jclass executorClass = nullptr;
  + jmethodID execute = nullptr;
  };
  void acquireCallbackJni(JNIEnv* env, CallbackJni& callbackUtils);
  