code: function ( that ) {
  		that = that || this;
  		var can = that.contentItems.length - that._isDocked() > 1;
  		for (var i = 0; i < that.contentItems.length; ++i )
  			if ( that.contentItems[ i ] instanceof lm.items.Stack ) {
  				that.contentItems[ i ].header._setDockable( that._isDocked( i ) || can );
  				that.contentItems[ i ].header._$setClosable( can );
  			}
  	}
docs: Validate if row or column has ability to dock
  @private