Bug: Fix red ImGui error window in combobox. Fix Duplicate case insensitive paths on Windows. Fix Nullptr deref.

src/opengl/main/generic_combo.hpp

@@ -1733,7 +1733,7 @@ class GenericCombo
                     // want, outside or inside your objects
                     if (std::ranges::empty(string))
                     {
-                         return;
+                         continue;
                     }
                     const char *c_str_value = std::ranges::data(string);
                     {

src/opengl/main/gui/gui.cpp

@@ -1206,7 +1206,7 @@ void gui::hovered_tiles_panel()
 }
 void gui::combo_coo()
 {
-     bool remaster = m_field->is_remaster_from_fl_paths();
+     bool remaster = m_field && m_field->is_remaster_from_fl_paths();
      if (!remaster)
      {
           return;
@@ -2447,7 +2447,7 @@ void gui::file_menu()
      {
           return;
      }
-     bool remaster = m_field->is_remaster_from_fl_paths();
+     bool remaster = m_field && m_field->is_remaster_from_fl_paths();
      if (remaster && ImGui::BeginMenu(gui_labels::language.data()))
      {
           const auto end_menu1         = glengine::ScopeGuard(&ImGui::EndMenu);
@@ -4245,7 +4245,8 @@ gui::gui(GLFWwindow *const window)
        });
 
      m_filter_window.register_is_remaster_callback(
-       [this]() -> bool { return m_field->is_remaster_from_fl_paths(); });
+       [this]() -> bool
+       { return m_field && m_field->is_remaster_from_fl_paths(); });
 
      if (m_field)
      {

src/opengl/main/utilities.hpp

@@ -56,12 +56,47 @@ concept erasable_range = std::ranges::range<R> && requires(R &r) {
      } -> std::same_as<typename R::iterator>;
 };
 
+inline std::filesystem::path
+  normalize_for_compare(const std::filesystem::path &p)
+{
+     auto norm = p.lexically_normal();
+
+#if defined(_WIN32)
+
+     // Windows: case-insensitive
+     auto s = norm.native();
+     std::ranges::transform(
+       s,
+       s.begin(),
+       [](const auto ch)
+       {
+            return static_cast<std::remove_cvref_t<decltype(ch)>>(
+              std::tolower(ch));
+       });
+     return std::filesystem::path{ s };
+#else
+     // Linux / others: case-sensitive
+     return norm;
+#endif
+}
+
 template<erasable_range... R>
 constexpr inline bool sort_and_remove_duplicates(R &...ranges) noexcept
 {
-     bool       changed = false;
-     const auto projection
-       = [](const auto &values) { return std::get<0>(values); };
+     bool       changed    = false;
+     const auto projection = [](const auto &values)
+     {
+          using value_t = std::remove_cvref_t<decltype(std::get<0>(values))>;
+
+          if constexpr (std::is_same_v<value_t, std::filesystem::path>)
+          {
+               return normalize_for_compare(std::get<0>(values));
+          }
+          else
+          {
+               return std::get<0>(values);
+          }
+     };
      auto zip_view = std::ranges::views::zip(ranges...);
      if (!std::ranges::is_sorted(zip_view, {}, projection))
      {