Crash when setting a tag Highlight color and accepting default, then navigating to said tab

[gmyx]

Steps to reproduce:

1. Manage Tags -> Edit a tag
2. Set highlight Color to Yes
3. DO not change the color (i.e. accept black)
4. Hit OK
5. Naviagate to that Tab. Crash below.

(Edit: you can 'undo' by changing the highlight color)

** Exception Text ** System.InvalidOperationException: Nullable object must have a value. at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at DoomLauncher.GameFileTile.SetData(IGameFile gameFile, IEnumerable1 tags) at DoomLauncher.GameFileTileExpanded.SetData(IGameFile gameFile, IEnumerable1 tags) at DoomLauncher.GameFileTileViewControl.SetTileData(GameFileTileBase tile, IGameFile gameFile, IEnumerable1 screenshots, IEnumerable1 thumbnails, IEnumerable1 tags, Boolean forceRefresh) at DoomLauncher.GameFileTileViewControl.SetLayout(List1 gameFiles, IEnumerable1 screenshots, IEnumerable1 thumbnails) at DoomLauncher.GameFileTileViewControl.SetPageData(Int32 pageIndex, Boolean dataChange) at DoomLauncher.GameFileTileViewControl.SetVisible(Boolean set) at DoomLauncher.MainForm.HandleTabSelectionChange() at DoomLauncher.MainForm.tabControl_SelectedIndexChanged(Object sender, EventArgs e) at System.Windows.Forms.TabControl.OnSelectedIndexChanged(EventArgs e) at System.Windows.Forms.TabControl.WmSelChange() at System.Windows.Forms.TabControl.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)