Plugin with FCKTextColorCommand

I have a problem with the FCKTextColorCommand command for a new pulldown-color-menu.
I want to use this command in a plugin.
I have made other plugins with no problems.
The content of fckplugin.js is:

FCKCommands.RegisterCommand ( 'daffie_bgcolor', new FCKTextColorCommand('Backcolor')) ;

var obgColorItem = new FCKToolbarPanelButton ( 'daffie_bgcolor', 'Daffie bgcolor', null, null, 46); FCKToolbarItems.RegisterItem ( 'daffie_bgcolor', obgColorItem ) ;


This plugin gives an error (a default error that the button does not work).

In the file fcktextcolorcommand.js is the function FCKTextColorCommand.
If I delete the following two lines of code in this function, then the plugin works perfectly.
After using the packager ofcourse.

else if ( FCK.ToolbarSet._IFrame )

oWindow = FCKTools.GetElementWindow( FCK.ToolbarSet._IFrame ) ;


Do I make a mistake or is this a bug?

Hope that somebody can help me.