#vulnerable code 
                                @Override
    protected String getApiRoute() {
        if (owner == null) {
            // Issues returned from search to do not have an owner. Attempt to use url.
            return StringUtils.prependIfMissing(getUrl().toString().replace(root.getApiUrl(), ""), "/");
        }
        return "/repos/" + owner.getOwnerName() + "/" + owner.getName() + "/pulls/" + number;
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    protected String getApiRoute() {
        if (owner == null) {
            // Issues returned from search to do not have an owner. Attempt to use url.
            final URL url = Objects.requireNonNull(getUrl(), "Missing instance URL!");
            return StringUtils.prependIfMissing(url.toString().replace(root.getApiUrl(), ""), "/");

        }
        return "/repos/" + owner.getOwnerName() + "/" + owner.getName() + "/pulls/" + number;
    }