Debug Tools: fixed assertion failure when opening a combo box while using io.ConfigDebugBeginReturnValueOnce/ConfigDebugBeginReturnValueLoop. (#8931)

docs/CHANGELOG.txt

@@ -85,6 +85,8 @@ Other Changes:
   is now skipped. (#8904, #4631)
 - Debug Tools: ID Stack Tool: added option to hex-encode non-ASCII characters in
   output path. (#8904, #4631)
+- Debug Tools: Fixed assertion failure when opening a combo box while using
+  io.ConfigDebugBeginReturnValueOnce/ConfigDebugBeginReturnValueLoop. (#8931) [@harrymander]
 - Demo: tweaked ShowFontSelector() and ShowStyleSelector() to update selection
   while navigating and to not close popup automatically.
 - Examples: Android: Android+OpenGL3: update Gradle project (#8888, #8878) [@scribam]

imgui_widgets.cpp

@@ -2032,7 +2032,8 @@ bool ImGui::BeginComboPopup(ImGuiID popup_id, const ImRect& bb, ImGuiComboFlags
     if (!ret)
     {
         EndPopup();
-        IM_ASSERT(0);   // This should never happen as we tested for IsPopupOpen() above
+        if (!g.IO.ConfigDebugBeginReturnValueOnce && !g.IO.ConfigDebugBeginReturnValueLoop) // Begin may only return false with those debug tools activated.
+            IM_ASSERT(0); // This should never happen as we tested for IsPopupOpen() above
         return false;
     }
     g.BeginComboDepth++;