Bug 121498 When datasource/dataset deleted, the datasource/dataset property binding element haven't been deleted
When deleted the datasource/dataset, the datasource/dataset property binding element haven't been deleted. Expected result: This operation must be a transaction.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DesignElementHandle.java
return null;
		if ( propDefn.getTypeCode( ) != PropertyType.DIMENSION_TYPE )
			return null;
		return new DimensionHandle( this, propDefn );
	}
	/**
	 * Returns a handle to work with a color property. Returns null if the given
	 * property is not defined or not color property.
	 * 
	 * @param propName
	 *            name of the property.
	 * @return a corresponding ColorHandle to with with the color property.
	 *         Return <code>null</code> if the given property is not defined
	 *         or not color property.
	 * 
	 * @see ColorHandle
	 */
	public ColorHandle getColorProperty( String propName )
	{
		ElementPropertyDefn propDefn = getElement( ).getPropertyDefn( propName );
		if ( propDefn == null )
			return null;
		if ( propDefn.getTypeCode( ) != PropertyType.COLOR_TYPE )
			return null;
		return new ColorHandle( this, propDefn );
	}
	/**
	 * Gets the font handle for the element. If this element defines a font
	 * family property, return a <code>FontHandle</code>. Otherwise, return
	 * <code>null</code>.