End() avoid calling Columns() if no columns set is open, not sure what it wasn't the case.

Pros: Faster. Avoid early crashes StackId underflow that are meant to be more gracefully caught by CheckStacksSize() (with more explicit assert). Cons: Excercise less code.

imgui.cpp

@@ -4434,7 +4434,8 @@ void ImGui::End()
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
 
-    Columns(1, "#CloseColumns");
+    if (window->DC.ColumnsCount != 1) // close columns set if any is open
+        Columns(1, "#CLOSECOLUMNS");
     PopClipRect();   // inner window clip rectangle
 
     // Stop logging