Fix crash from model edits while viewport is disabled

Switch_FileFormatsMain/GUI/BFRES/BfresEditor.cs

@@ -56,7 +56,7 @@ namespace FirstPlugin.Forms
                     return null;
 
                 var editor = LibraryGUI.Instance.GetObjectEditor();
-               return editor.GetViewport();
+                return editor.GetViewport();
             }
             set
             {
@@ -157,11 +157,11 @@ namespace FirstPlugin.Forms
 
         public void AddDrawable(AbstractGlDrawable draw)
         {
-            if (!Runtime.UseViewport)
-                return;
-
             Drawables.Add(draw);
 
+            if (!Runtime.UseViewport || !Runtime.DisplayViewport)
+                return;
+
             if (!viewport.scene.staticObjects.Contains(draw) &&
                 !viewport.scene.objects.Contains(draw))
             {
@@ -171,10 +171,11 @@ namespace FirstPlugin.Forms
 
         public void RemoveDrawable(AbstractGlDrawable draw)
         {
-            if (!Runtime.UseViewport)
+            Drawables.Remove(draw);
+
+            if (!Runtime.UseViewport || !Runtime.DisplayViewport)
                 return;
 
-            Drawables.Remove(draw);
             viewport.RemoveDrawable(draw);
         }