Popups: Fixed right-click to close popups not handling modal windows properly. (~#439)

imgui_demo.cpp

@@ -1453,6 +1453,8 @@ void ImGui::ShowTestWindow(bool* p_open)
                 ImGui::Text("Hello from Stacked The First\nUsing style.Colors[ImGuiCol_ModalWindowDarkening] for darkening.");
                 static int item = 1;
                 ImGui::Combo("Combo", &item, "aaaa\0bbbb\0cccc\0dddd\0eeee\0\0");
+                static float color[4] = { 0.4f,0.7f,0.0f,0.5f };
+                ImGui::ColorEdit4("color", color);  // This is to test behavior of stacked regular popups over a modal
 
                 if (ImGui::Button("Add another modal.."))
                     ImGui::OpenPopup("Stacked 2");