#vulnerable code 
                             public static HalLinkRelation of(@Nullable LinkRelation relation) {

		Assert.notNull(relation, "LinkRelation must not be null!");

		if (HalLinkRelation.class.isInstance(relation)) {
			return HalLinkRelation.class.cast(relation);
		}

		return of(relation.value());
	} 
                            #location 9 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             public static HalLinkRelation of(@Nullable LinkRelation relation) {

		Assert.notNull(relation, "LinkRelation must not be null!");

		if (relation instanceof HalLinkRelation) {
			return (HalLinkRelation) relation;
		}

		return of(relation.value());
	}