- made load game failure a bit more resilient

https://www.doomworld.com/forum/topic/111069-savestate-problems-with-gzdoom/

src/events.cpp

@@ -1264,7 +1264,8 @@ void DStaticEventHandler::NewGame()
 //
 void DStaticEventHandler::OnDestroy()
 {
-	owner->UnregisterHandler(this);
+	if (owner)
+		owner->UnregisterHandler(this);
 	Super::OnDestroy();
 }
 

src/r_data/r_interpolate.cpp

@@ -355,7 +355,8 @@ int DInterpolation::DelRef(bool force)
 
 void DInterpolation::UnlinkFromMap()
 {
-	Level->interpolator.RemoveInterpolation(this);
+	if (Level)
+		Level->interpolator.RemoveInterpolation(this);
 	refcount = 0;
 }