Docking: Fixed assert preventing dockspace from being stored into a tab. (#3101)

imgui_widgets.cpp

@@ -6849,7 +6849,7 @@ void ImGui::TabBarAddTab(ImGuiTabBar* tab_bar, ImGuiTabItemFlags tab_flags, ImGu
 {
     ImGuiContext& g = *GImGui;
     IM_ASSERT(TabBarFindTabByID(tab_bar, window->ID) == NULL);
-    IM_ASSERT(g.CurrentTabBar == NULL);                     // Can't work while the tab bar is active as our tab doesn't have an X offset yet
+    IM_ASSERT(g.CurrentTabBar != tab_bar);  // Can't work while the tab bar is active as our tab doesn't have an X offset yet, in theory we could/should test something like (tab_bar->CurrFrameVisible < g.FrameCount) but we'd need to solve why triggers the commented early-out assert in BeginTabBarEx() (probably dock node going from implicit to explicit in same frame)
 
     ImGuiTabItem new_tab;
     new_tab.ID = window->ID;