Add missing null check

Author: Rampastring

src/TSMapEditor/UI/UIManager.cs

@@ -335,6 +335,9 @@ private void InitNotificationManager()
 
         private void SetNotificationManagerSizeAndPosition()
         {
+            if (notificationManager == null)
+                return;
+
             notificationManager.X = editorSidebar.X + Constants.UIEmptySideSpace;
             notificationManager.Width = WindowManager.RenderResolutionX - (notificationManager.X * 2);
             notificationManager.Y = 100;

src/TSMapEditor/UI/Windows/HousesWindow.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Globalization;
 using System.Linq;
-using TSMapEditor.Initialization;
 using TSMapEditor.Models;
 using TSMapEditor.UI.Controls;