Assert.isTrue(isCustomFilter());
if (!isCustomFilter()) return null;
	public ViewerFilter createViewerFilter() {		Assert.isTrue(isCustomFilter());		ViewerFilter result= null;		try {			result= (ViewerFilter)fElement.createExecutableExtension(CLASS_ATTRIBUTE);		} catch (CoreException ex) {			handleError(ex.getStatus());		} catch (ClassCastException ex) {			handleError(new Status(IStatus.ERROR, JavaUI.ID_PLUGIN, IJavaStatusConstants.INTERNAL_ERROR, ex.getLocalizedMessage(), ex));		// Workaround for http://bugs.eclipse.org/bugs/show_bug.cgi?id=37215		} catch (NoClassDefFoundError ex) {			handleError(new Status(IStatus.ERROR, JavaUI.ID_PLUGIN, IJavaStatusConstants.INTERNAL_ERROR, ex.getLocalizedMessage(), ex));		}		return result;	}