Bug 140395 IImage.getID() return null on chart images
When I use image.getID() to retrieve ID of chart image, it always returns null.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/Image.java
* 
	 * @param data
	 * @param name
	 */
	public Image( byte[] data, String name )
	{
		if ( data == null )
		{
			return;
		}
		id = name;
		this.data = data;
		this.source = IImage.CUSTOM_IMAGE;
	}
	public Image( IImageContent content )
	{
		String imgUri = content.getURI( );
		byte[] imgData = content.getData( );
		extension = content.getExtension( );
		if ( extension == null )
		{
			String mimeType = content.getMIMEType( );
			if ( mimeType != null )
			{
				extension = FileUtil.getExtFromType( mimeType );
			}
		}
		switch ( content.getImageSource( ) )
		{
			case IImageContent.IMAGE_FILE :