BeginPopupModal(): the conditional test for SetNextWindowPos() was polling the wrong window, which in practice made the test succeed all the time.

imgui.cpp

@@ -3885,7 +3885,7 @@ bool ImGui::BeginPopupModal(const char* name, bool* p_open, ImGuiWindowFlags ext
     }
 
     // Center modal windows by default
-    if ((window->SetWindowPosAllowFlags & g.SetNextWindowPosCond) == 0)
+    if (g.SetNextWindowPosCond == 0)
         SetNextWindowPos(g.IO.DisplaySize * 0.5f, ImGuiCond_Appearing, ImVec2(0.5f, 0.5f));
 
     ImGuiWindowFlags flags = extra_flags|ImGuiWindowFlags_Popup|ImGuiWindowFlags_Modal|ImGuiWindowFlags_NoCollapse|ImGuiWindowFlags_NoSavedSettings;