Bug 142137 Style name can't be changed to None in Property Editor after delete the style
Steps to reproduce: 1.New a style named "S1", apply it on a label 2.Delete "S1" 3.Switch to Property Editor, change label style to None Expected result: Style is changed to None Actual result: Style is still "S1" till change it with context menu
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/StyleCommand.java
.getPropertyDefn( IStyledElementModel.STYLE_PROP );
		if ( name == null && obj.getStyleName( ) == null )
			return;
		Object retValue = null;
		try
		{
			retValue = propDefn.validateValue( module, name );
		}
		catch ( PropertyValueException e )
		{
			assert false;
		}
		
		doSetStyleRefValue( (ElementRefValue) retValue );
	}
	/**
	 * Sets the style of an element given the style itself.
	 * 
	 * @param style
	 *            the style element to set.
	 * @throws StyleException
	 *             if the element can not have style or the style is not found.
	 */
	public void setStyleElement( DesignElement style ) throws StyleException
	{
		
		
		
		String name = null;
		if ( style != null )