Frontend-GNOME: handle DllNotFoundException in MenuWidget on macOS

The Mono runtime on macOS might not have the libigemacintegration.dylib
library present at all, which then leads to the DllNotFoundException.

Instead of crashing we handle that exception the same way as
EntryPointNotFoundException and gracefully continue.

src/Frontend-GNOME/Views/MenuWidget.cs

@@ -164,8 +164,8 @@ public MenuWidget(Gtk.Window parent, ChatViewManager chatViewManager)
  f_SmuxiAction.Visible = false;
  // About item is already shown in app menu
  f_AboutAction.Visible = false;
- } catch (EntryPointNotFoundException ex) {
- f_Logger.Error("Failed to initialize mac menu integration, disabling mac menu integration", ex);
+ } catch (Exception ex) when (ex is DllNotFoundException || ex is EntryPointNotFoundException) {
+ f_Logger.Error("Failed to initialize macOS menu integration, disabling integration...", ex);
  }
  }
  }