Bug 214212 Problem occurs when set the masterpage margin with ems/exs/pixcel units.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/metadata/DimensionPropertyType.java
* 
	 * @param module
	 *            the report design
	 * @param defn
	 *            property definition.
	 * @param value
	 *            the dimension value of the dimension.
	 * @throws PropertyValueException
	 *             if unit is not allowed.
	 * 
	 */
	private void validateUnits( Module module, PropertyDefn defn,
			DimensionValue value ) throws PropertyValueException
	{
		assert value != null;
		String unit = value.getUnits( );
		if ( DimensionValue.DEFAULT_UNIT.equalsIgnoreCase( unit ) )
		{
			unit = getDefaultUnit( module, defn );
		}
		IChoiceSet units = defn.getAllowedUnits( );
		assert units != null;
		if ( !StringUtil.isBlank( unit ) && !units.contains( unit ) )
		{
			
			logger.log( Level.SEVERE, "unit:" + unit + " not allowed " ); 
			throw new PropertyValueException( null, defn, value,
					PropertyValueException.DESIGN_EXCEPTION_UNIT_NOT_ALLOWED );
		}
	}