Bug 167545 Copy a cascading parameter group and paste it to another parameter group causes an exception thrown
Steps to reproduce: 1.Copy a cascading parameter group using short cut key "Ctrl+x"/"Ctrl+c", or choosing context menu "Cut"/"Copy"; 2.Paste it to another parameter group using short cut key "Ctrl+v", or choosing context menu "Paste"; Expected result: The source one is pasted in the destination. Actual result: An exception thrown org.eclipse.birt.report.model.api.command.ContentException: The Cascading Parameter Group("Source") is not allowed in the slot (parameters) of Parameter Group("Destination").
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
else if( input instanceof List ){
			GroupElementHandle group = DEUtil.getGroupElementHandle( (List)input );
			if(notSame && group!=null && group.isSameType( ) ) return null;
			return  ((List)input).get( 0 );
		}
		else return input;
	}
	
	public static Object getInputElement(Object input,int index){
		if ( input instanceof GroupElementHandle )
		{
			return  ( (GroupElementHandle) input ).getElements( ).get( index );
		}
		else if( input instanceof List ){
			return  ((List)input).get( index );
		}
		else return input;
	}
	
	public static List getInputElements(Object input){
		if ( input instanceof GroupElementHandle )
		{
			return  ( (GroupElementHandle) input ).getElements( );
		}
		else if( input instanceof List ){
			return  (List)input;
		}
		else return Collections.EMPTY_LIST;
	}
}