fix virtual asset leak

Source/Game/Level/Q3MapImporter.cs

@@ -325,7 +325,7 @@ public class Q3MapImporter : Script
         Editor.Instance.PlayModeBeginning -= OnEditorPlayModeStart;
         Editor.Instance.PlayModeEnd -= OnEditorPlayModeEnd;
 
-        //UnloadMap();
+        UnloadMap();
     }
 #endif
     public override void OnStart()
@@ -728,6 +728,8 @@ public class Q3MapImporter : Script
                     mesh.normals.Add(normal);
                 }
 
+                if (!LoadCollidersOnly)
+                {
                 geom.model = Content.CreateVirtualAsset<Model>();
                 geom.model.SetupLODs(new[] { geom.meshes.Length });
                 geom.model.SetupMaterialSlots(geom.meshes.Length);
@@ -746,6 +748,7 @@ public class Q3MapImporter : Script
 
                 //Not supported yet, should be done here
                 //geom.model.GenerateSDF();
+                }
 
                 brushIndex++;
             }