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
Collection derived = obj.getDerived( );
		if ( derived.isEmpty( ) )
			return;
		DesignElement parent = obj.getExtendsElement( );
		Iterator iter = derived.iterator( );
		while ( iter.hasNext( ) )
		{
			DesignElement child = (DesignElement) iter.next( );
			ExtendsCommand childCmd = new ExtendsCommand( module, child );
			childCmd.setExtendsElement( parent );
		}
	}
	/**
	 * Adjusts references to an element that is to be deleted. The element to be
	 * deleted is one that has references in the form of element reference
	 * properties on other elements. These other elements, called "clients",
	 * each contain a property of type element reference and that property
	 * refers to this element. Each reference is recorded with a "back pointer"
	 * from the referenced element to the client. That back pointer has both a
	 * pointer to the client element, and the property within that element that
	 * holds the reference. There are two algorithms to handle this reference
	 * property, which can be selected by <code>unresolveReference</code>. If
	 * <code>unresolveReference</code> is <code>true</code>, the reference
	 * property is unresolved. Otherwise, it's cleared.
	 * 
	 * @param referred
	 *            the element to be deleted
	 * @param unresolveReference
	 *            the flag indicating the reference property should be
	 *            unresolved, instead of cleared