Bug 195607 NPE is thrown when calling DimensionHandle:: getAbsoluteValue()
If a DimensionHandle did not set DimensionValue, NPE will thrown when calling DimensionHandle:: getAbsoluteValue().
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/FontSizeValueHandler.java
* <ul>
	 * <li><code>FONT_SIZE_XX_SMALL</code>
	 * <li><code>FONT_SIZE_X_SMALL</code>
	 * <li><code>FONT_SIZE_SMALL</code>
	 * <li><code>FONT_SIZE_MEDIUM</code>
	 * <li><code>FONT_SIZE_LARGE</code>
	 * <li><code>FONT_SIZE_X_LARGE</code>
	 * <li><code>FONT_SIZE_XX_LARGE</code>
	 * </ul>
	 * 
	 * <p>
	 * For example,
	 * <p>
	 * <ul>
	 * <li>The absolute base font size constant is "MEDIUM", and the relative
	 * one "LARGER" is converted to "LARGE".
	 * <li>The absolute base font size constant is "XX_SMALL", and the relative
	 * one "SMALLER" is converted to "XX_SMALL".
	 * </ul>
	 * 
	 * @param relativeConstant
	 *            the relative constant to convert
	 * @param baseConstant
	 *            the base constant on which this conversion is based
	 * @return the absolute font size constant
	 */
	private String convertRelativeConstantToAbsolute( String relativeConstant,
			String baseConstant )
	{
		for ( int i = 0; i < ABSOLUTE_FONT_SIZE_CONSTANTS.length; i++ )