It looks like you are trying to reference something that is no-longer there. As suggested by Schdek it is worth testing for a NULL reference, but then also check if it is valid
if (StaticMeshComp && StaticMeshComp->IsValidLowLevel())
{
StaticMeshComp->SetRelativeLocation(...);
}
In your example it looks like StaticMeshComp would be being set to a non-NULL value (0xFFFFFFFFFFFFFFFF) so the test for NULL will pass, as the value isn’t NULL. The IsValidLowLevel should check that the reference is valid and whatever it points too checks out.
HTH