Bug 193886 NPE is thrown when preview external CSS style in ppt[1205]
engine/org.eclipse.birt.report.engine.emitter.ppt/src/org/eclipse/birt/report/engine/emitter/ppt/PPTRender.java
* @param x
	 *            the start X coordinate at the PPT where the image is
	 *            positioned
	 * @param y
	 *            the start Y coordinate at the PPT where the image is
	 *            positioned
	 * @param width
	 *            the width of the background dimension
	 * @param height
	 *            the height of the background dimension
	 * @param positionX
	 *            the offset X percentage relating to start X
	 * @param positionY
	 *            the offset Y percentage relating to start Y
	 * @param repeat
	 *            the background-repeat property
	 * @param xMode
	 *            whether the horizontal position is a percentage value or not
	 * @param yMode
	 *            whether the vertical position is a percentage value or not
	 */
	private void drawBackgroundImage( String imageURI, double x, double y,
			double width, double height, double positionX, double positionY,
			String repeat, boolean xMode, boolean yMode )
	{
		
		if ( imageURI == null || imageURI.length( ) == 0 )
		{
			return;
		}