message: [ncp] initialize OT instance to nullptr in the constructor
diff: @@ -64,7 +64,8 @@ namespace Ncp {
  ControllerOpenThread::ControllerOpenThread(const char *aInterfaceName,
  const char *aRadioUrl,
  const char *aBackboneInterfaceName)
  - : mTriedAttach(false)
  + : mInstance(nullptr)
  + , mTriedAttach(false)
  {
  memset(&mConfig, 0, sizeof(mConfig));
  