Scrollbar: Avoid rendering when sizes are negative to reduce glitches (not sure how this ever slipped through - perhaps because of WindowMinSize settings).

imgui.cpp

@@ -4474,6 +4474,8 @@ static void Scrollbar(ImGuiWindow* window, bool horizontal)
         : ImRect(window_rect.Max.x - style.ScrollbarSize, window->Pos.y + border_size, window_rect.Max.x - border_size, window_rect.Max.y - other_scrollbar_size_w - border_size);
     if (!horizontal)
         bb.Min.y += window->TitleBarHeight() + ((window->Flags & ImGuiWindowFlags_MenuBar) ? window->MenuBarHeight() : 0.0f);
+    if (bb.GetWidth() <= 0.0f || bb.GetHeight() <= 0.0f)
+        return;
 
     float window_rounding = (window->Flags & ImGuiWindowFlags_ChildWindow) ? style.ChildWindowRounding : style.WindowRounding;
     int window_rounding_corners;