fix default value vcard

Author: giauphan

src/QRCodeFactory.php

@@ -59,7 +59,7 @@ public function calendar(\DateTime $start, \DateTime $end, string $summary, stri
  */
  public function email(string $toEmail, string $body, string $subject): QR_EmailMessage
  {
- if (trim($toEmail) === '') {
+ if (trim($toEmail) === null) {
  throw new EmptyTextException('Recipient email cannot be empty');
  }
 
@@ -117,7 +117,7 @@ public function sms(string $number, string $text): QR_Sms
  */
  public function text(string $data): QR_Text
  {
- if (trim($data) === '') {
+ if (trim($data) === null) {
  throw new EmptyTextException('Text cannot be empty');
  }
 
@@ -135,7 +135,7 @@ public function text(string $data): QR_Text
  */
  public function url(string $url = null): QR_Url
  {
- // if (trim($url) === '') {
+ // if (trim($url) === null) {
  // throw new EmptyTextException('Url cannot be empty');
  // }
 
@@ -167,7 +167,7 @@ public function url(string $url = null): QR_Url
  * @throws \QR_Code\Exceptions\InvalidVCardAddressEntryException
  * @throws \QR_Code\Exceptions\InvalidVCardPhoneEntryException
  */
- public function vCard(string $firstName = null, string $lastName = null, string $title = '', string $email = '', string $company = '',string $job = '',string $url = '', array $addresses = [], array $phones = []): QR_VCard
+ public function vCard(string $firstName = null, string $lastName = null, string $title = null, string $email = null, string $company = null,string $job = null,string $url = null, array $addresses = [], array $phones = []): QR_VCard
  {
  // $this->validateVCardAddresses($addresses);
  // $this->validatePrefAddresses($addresses);