Bug 149251 Inconsistent Handling of a Non-inheritable ROM Property
For a ROM property defined to be non-inheritable, an empty string property value should be consistently handled as an empty string, not as null. For example, an oda.dataSource extension defines a data source property with canInherit=false. When a oda-data-source handle get saved in a report design, it correctly includes the tag for such property, even when an empty string value is specified. <oda-data-source extensionID="my.oda.plugin" name="my Data Source" id="24"> ... <property name="ApplicationServer"></property> </oda-data-source> However, later when using the DE API to read its property value, a null is returned. Then when the report design is subsequently saved, the property tag is lost. Expects that an empty string value of a non-inhertiable property should be preserved.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* 
	 * @param slotID
	 *            slot id
	 * @return the selector of the given slot of this element.
	 */
	public String getSelector( int slotID )
	{
		ElementDefn defn = (ElementDefn) getDefn( );
		SlotDefn slotDefn = (SlotDefn) defn.getSlot( slotID );
		if ( slotDefn == null )
		{
			return null;
		}
		String slotSelector = slotDefn.getSelector( );
		if ( StringUtil.isBlank( slotSelector ) )
		{
			return null;
		}
		return slotSelector;
	}
	/**
	 * Returns the property value.
	 * 
	 * @param module
	 *            the module
	 * @param prop
	 *            the definition of property
	 * @return the property value, or null if no value is set.
	 */
	public Object getProperty( Module module, PropertyDefn prop )