Unhandled exception, value cannot be null when opening Type Explorer

[Gama11]

I get this occassionally when pressing Ctrl+N to open the type explorer (custom shortcut). Haven't managed to reproduce it consistently.

See the end of this message for details on invoking 
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.ArgumentNullException: Value cannot be null.
Parameter name: key
   at System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at QuickNavigate.Forms.TypeExplorerForm.<CreateItemsList>b__18_0(FileModel model)
   at ASCompletion.Model.PathModel.ForeachFile(ForeachDelegate callback)
   at QuickNavigate.Forms.TypeExplorerForm.CreateItemsList()
   at QuickNavigate.Forms.TypeExplorerForm..ctor(Settings settings)
   at QuickNavigate.PluginMain.ShowTypeExplorer(Object sender, EventArgs e)
   at System.Windows.Forms.ToolStripItem.RaiseEvent(Object key, EventArgs e)
   at System.Windows.Forms.ToolStripMenuItem.OnClick(EventArgs e)
   at System.Windows.Forms.ToolStripItem.HandleClick(EventArgs e)
   at System.Windows.Forms.ToolStripItem.FireEventInteractive(EventArgs e, ToolStripItemEventType met)
   at System.Windows.Forms.ToolStripItem.FireEvent(EventArgs e, ToolStripItemEventType met)
   at System.Windows.Forms.ToolStripMenuItem.ProcessCmdKey(Message& m, Keys keyData)
   at System.Windows.Forms.ToolStripManager.ProcessShortcut(Message& m, Keys shortcut)
   at System.Windows.Forms.ToolStripManager.ProcessCmdKey(Message& m, Keys keyData)
   at System.Windows.Forms.ContainerControl.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Form.ProcessCmdKey(Message& msg, Keys keyData)
   at FlashDevelop.MainForm.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.ContainerControl.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.ContainerControl.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Form.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.ContainerControl.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.ProcessCmdKey(Message& msg, Keys keyData)
   at System.Windows.Forms.Control.PreProcessMessage(Message& msg)
   at ScintillaNet.ScintillaControl.PreProcessMessage(Message& m)
   at System.Windows.Forms.Control.PreProcessControlMessageInternal(Control target, Message& msg)
   at System.Windows.Forms.Application.ThreadContext.PreTranslateMessage(MSG& msg)

[SlavaRa]

I will correct this error after the main work, sorry.