Bug 124620 Referenced Parameter icon should be invalid if the parameter in library is deleted
Description: Referenced parameter icon should be invalid if the source parameter in library is deleted. Steps to reproduce: 1.Create a library. Insert a report scalar parameter. 2.Create a report, use the above library. In the library explorer, pull the parameter to the data explorer view of report. 3.Open the library file, delete the parameter. Then reopen the report design file, the icon of parameter seems nothing happened. But if those operations happened in dataset, the icon of dataset in the report will be invalid. It is acceptable. Expected Result: The icon of referenced parameter should be invalid.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
*            the name of the property to get
	 * @return the property value as a double. Returns 0 if the property is not
	 *         defined, or cannot convert to a double.
	 */
	public double getFloatProperty( Module module, String propName )
	{
		ElementPropertyDefn prop = getPropertyDefn( propName );
		if ( prop == null )
			return 0;
		PropertyType type = MetaDataDictionary.getInstance( ).getPropertyType(
				prop.getTypeCode( ) );
		Object value = getProperty( module, propName );
		if ( value instanceof Double )
			return ( (Double) value ).doubleValue( );
		return type.toDouble( module, value );
	}
	/**
	 * Gets the value of a property as a boolean.
	 * 
	 * @param module
	 *            the module
	 * @param propName
	 *            the name of the property to get
	 * @return the property value as a boolean. Returns false if the property is
	 *         not set, or not defined, or cannot convert to a boolean.
	 */
	public boolean getBooleanProperty( Module module, String propName )
	{
		ElementPropertyDefn prop = getPropertyDefn( propName );
		if ( prop == null )