Added temporary storage of guids of collections to be wiped on bootup when crash/reload (#109)

Co-authored-by: cake <admin@cakeandbanana.nl>
Reviewed-on: #109
Reviewed-by: defnotken <defnotken@noreply.git.lightless-sync.org>

LightlessSync/UI/DownloadUi.cs

@@ -178,6 +178,11 @@ public class DownloadUi : WindowMediatorSubscriberBase
         foreach (var transfer in transfers)
         {
             var transferKey = transfer.Key;
+
+            // Skip if no valid game object
+            if (transferKey.GetGameObject() == null)
+                continue;
+
             var rawPos = _dalamudUtilService.WorldToScreen(transferKey.GetGameObject());
 
             // If RawPos is zero, remove it from smoothed dictionary