Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/PropertyCommand.java
.equals( propName ) ) )
			{
				throw new SemanticError( element,
						SemanticError.DESIGN_EXCEPTION_CANNOT_SPECIFY_PAGE_SIZE );
			}
		}
		value = validateValue( prop, value );
		if ( element instanceof GroupElement
				&& GroupElement.GROUP_NAME_PROP.equals( prop.getName( ) ) )
		{
			if ( !isGroupNameValidInContext( (String) value ) )
				throw new NameException( element, (String) value,
						NameException.DESIGN_EXCEPTION_DUPLICATE );
		}
		
		if ( prop.isIntrinsic( ) )
		{
			setIntrinsicProperty( prop, value );
		}
		else
		{
			doSetProperty( prop, value );
		}
	}
	/**
	 * Private method to set property.
	 * 
	 * @param prop
	 *            the definition of the property to set.
	 * @param value