Bug 121864 Report element can't be deleted
Description: Report element can't be deleted Steps to reproduce: 1.Open the attached design file 2.Delete the table/parameters/dataset/datasource Expected result: The element can be deleted Actual result: They can't be deleted
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/ContentCommand.java
if ( to.isContentOf( content ) )
			throw new ContentException( to, fromSlotID, content,
					ContentException.DESIGN_EXCEPTION_RECURSIVE );
		
		if ( !element.getDefn( ).isContainer( ) )
			throw new ContentException( element, fromSlotID,
					ContentException.DESIGN_EXCEPTION_NOT_CONTAINER );
		if ( !to.getDefn( ).isContainer( ) )
			throw new ContentException( to, toSlotID,
					ContentException.DESIGN_EXCEPTION_NOT_CONTAINER );
		ContainerSlot fromSlot = element.getSlot( fromSlotID );
		if ( fromSlot == null )
			throw new ContentException( element, fromSlotID,
					ContentException.DESIGN_EXCEPTION_SLOT_NOT_FOUND );
		ContainerSlot toSlot = to.getSlot( toSlotID );
		if ( toSlot == null )
			throw new ContentException( to, toSlotID,
					ContentException.DESIGN_EXCEPTION_SLOT_NOT_FOUND );
		if ( !fromSlot.contains( content ) )
			throw new ContentException( element, fromSlotID, content,
					ContentException.DESIGN_EXCEPTION_CONTENT_NOT_FOUND );
		if ( !fromSlot.canDrop( content ) )
			throw new ContentException( element, fromSlotID, content,
					ContentException.DESIGN_EXCEPTION_DROP_FORBIDDEN );
		
		
		if ( hasDescendents( content, fromSlotID ) )
		{
			throw new ContentException( element, fromSlotID,