message: Destroy Ceed context in Device destructor
  Also inititalize internal::ceed to NULL
diff: @@ -33,7 +33,7 @@ occa::device occaDevice;
  #endif
  #ifdef MFEM_USE_CEED
  -Ceed ceed;
  +Ceed ceed = NULL;
  #endif
  // Backends listed by priority, high to low:
  @@ -66,6 +66,9 @@ Device::~Device()
  if (destroy_mm)
  {
  free(ceed_option);
  +#ifdef MFEM_USE_CEED
  + CeedDestroy(&internal::ceed);
  +#endif
  mm.Destroy();
  }
  }
  