Bug #66103 cannot edit tables after switching between different tables.

Description:
I try to edit tables, and after switching between a few tables, I get an error "unable to cast object of type 'MySQL.Forms.MenuItemImpl' to type 'MySQL.GUI.Workbench.Plugins.DockalePlugin'.

----- Developer Notes -----

MySQL Workbench CE for Windows version 5.2.41  revision 9727
Configuration Directory: C:\Documents and Settings\Administrator\Application Data\MySQL\Workbench
Data Directory: C:\Program Files\MySQL\MySQL Workbench 5.2 CE
Cairo Version: 1.8.8
OS: Microsoft Windows XP Professional Service Pack 3 (build 2600)
CPU: 2x Intel(R) Pentium(R) 4 CPU 2.80GHz, 1.0 GiB RAM
Active video adapter (0): Intel(R) 82915G/GV/910GL Express Chipset Family
Installed video RAM: 128 MB
Current video mode: 1280 x 768 x 4294967296 colors
Used bit depth: 32
Driver version: 6.14.10.4020
Installed display drivers: ialmrnt5.dll
Current user language: English (United States)

Exception = System.InvalidCastException
Message = Unable to cast object of type 'MySQL.Forms.MenuItemImpl' to type 'MySQL.GUI.Workbench.Plugins.DockablePlugin'.
FullText = System.InvalidCastException: Unable to cast object of type 'MySQL.Forms.MenuItemImpl' to type 'MySQL.GUI.Workbench.Plugins.DockablePlugin'.
   at MySQL.GUI.Workbench.Plugins.DockablePlugin.GetFromFixedPtr(IntPtr ptr)
   at MySQL.GUI.Workbench.MainForm.ShowPlugin(IntPtr ptr)
   at MySQL.Forms.AppImpl.show_editor_wrapper(UInt32 native_handle)
   at boost.detail.function.void_function_invoker1<void (__cdecl*)(unsigned int),void,unsigned int>.invoke(function_buffer* function_ptr, UInt32 a0)
   at MySQL.Grt.ListModel.activate_node(NodeId node)
   at MySQL.GUI.Workbench.ModelOverviewForm.listViewDoubleClick(Object sender, EventArgs e)
   at System.Windows.Forms.Control.OnDoubleClick(EventArgs e)
   at System.Windows.Forms.ListView.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)

How to repeat:
create several tables, then switch between them to view and make changes.

This is a duplicate of bug #66013.