Popups: similarly to previous commit, we fix reopening a popup within a popup stack from truncating the whole stack. This is done by properly refocusing the lower level popup. (~#439)

imgui.cpp

@@ -3567,6 +3567,11 @@ void ImGui::OpenPopupEx(ImGuiID id, bool reopen_existing)
     {
         g.OpenPopupStack.resize(current_stack_size+1);
         g.OpenPopupStack[current_stack_size] = popup_ref;
+
+        // When reopening a popup we first refocus its parent, otherwise if its parent is itself a popup it would get closed by CloseInactivePopups().
+        // This is equivalent to what ClosePopupToLevel() does.
+        if (g.OpenPopupStack[current_stack_size].PopupId == id)
+            FocusWindow(window);
     }
 }