Docking: fixed potential crash if a passthrough dock node is submitted without a child intermediate (currently not possible via API)

imgui.cpp

@@ -14979,7 +14979,8 @@ static void ImGui::DockNodeUpdate(ImGuiDockNode* node)
         if (central_node_hole && !hole_rect.IsInverted())
         {
             SetWindowHitTestHole(host_window, hole_rect.Min, hole_rect.Max - hole_rect.Min);
-            SetWindowHitTestHole(host_window->ParentWindow, hole_rect.Min, hole_rect.Max - hole_rect.Min);
+            if (host_window->ParentWindow)
+                SetWindowHitTestHole(host_window->ParentWindow, hole_rect.Min, hole_rect.Max - hole_rect.Min);
         }
     }