Fixed syncing null Designation/DesignationManager

I haven't considered how map syncing works when writing those 2 sync worker delegates, and made an error in the way they handle maps.

Specifically, the issue here is that writing a null map may result in a non-null map when reading if another sync worker is syncing the map. Likewise, I believe attempting to sync a null map may have set the map to null for a different sync worker delegate, causing issues there.

The change here is to, rather than sync the map itself (which we may have potentially synced as null and caused issues for other sync workers) we instead sync a bool that determines if the manager is null or has null map (and we then set the MpContext to use its map).

Source/Client/Syncing/Dict/SyncDictRimWorld.cs

@@ -667,12 +667,18 @@ public static class SyncDictRimWorld
                 }
             },
             {
-                (SyncWorker sync, ref DesignationManager manager) =>
+                (ByteWriter data, DesignationManager manager) =>
                 {
-                    if (sync.isWriting)
-                        sync.Write(manager?.map);
-                    else
-                        manager = sync.Read<Map>()?.designationManager;
+                    var isNull = manager?.map == null;
+                    data.WriteBool(isNull);
+                    if (!isNull)
+                        data.MpContext().map = manager.map;
+                },
+                (ByteReader data) =>
+                {
+                    if (data.ReadBool())
+                        return null;
+                    return data.MpContext().map.designationManager;
                 }
             },
             {