Don't serialize meta fields if they're null [MAILPOET-2073]

lib/Models/ScheduledTask.php

@@ -99,7 +99,7 @@ class ScheduledTask extends Model {
     if (!$this->priority) {
       $this->priority = self::PRIORITY_MEDIUM;
     }
-    if (!Helpers::isJson($this->meta)) {
+    if (!is_null($this->meta) && !Helpers::isJson($this->meta)) {
       $this->set(
         'meta',
         json_encode($this->meta)

lib/Models/SendingQueue.php

@@ -16,7 +16,7 @@ if (!defined('ABSPATH')) exit;
  * @property string $newsletter_rendered_subject
  * @property int $task_id
  * @property int $newsletter_id
- * @property string|object $meta
+ * @property string|object|null $meta
  * @property string|array $subscribers
  * @property string|null $deleted_at
  */
@@ -77,7 +77,7 @@ class SendingQueue extends Model {
         json_encode($this->encodeEmojisInBody($this->newsletter_rendered_body))
       );
     }
-    if (!Helpers::isJson($this->meta)) {
+    if (!is_null($this->meta) && !Helpers::isJson($this->meta)) {
       $this->set(
         'meta',
         json_encode($this->meta)

tests/integration/Models/ScheduledTaskTest.php

@@ -125,6 +125,18 @@ class ScheduledTaskTest extends \MailPoetTest {
     expect(json_decode($task->meta, true))->equals($meta);
   }
 
+  function testItDoesNotJsonEncodesMetaEqualToNull() {
+    $task = ScheduledTask::create();
+    $meta = null;
+    $task->meta = $meta;
+    $task->save();
+
+    $task = ScheduledTask::findOne($task->id);
+
+    expect(Helpers::isJson($task->meta))->false();
+    expect($task->meta)->equals($meta);
+  }
+
   function _after() {
     \ORM::raw_execute('TRUNCATE ' . ScheduledTask::$_table);
     \ORM::raw_execute('TRUNCATE ' . ScheduledTaskSubscriber::$_table);

tests/integration/Models/SendingQueueTest.php

@@ -113,6 +113,20 @@ class SendingQueueTest extends \MailPoetTest {
     expect(json_decode($queue->meta, true))->equals($meta);
   }
 
+  function testItDoesNotJsonEncodesMetaEqualToNull() {
+    $queue = SendingQueue::create();
+    $meta = null;
+    $queue->task_id = 0;
+    $queue->newsletter_id = 1;
+    $queue->meta = $meta;
+    $queue->save();
+
+    $queue = SendingQueue::findOne($queue->id);
+
+    expect(Helpers::isJson($queue->meta))->false();
+    expect($queue->meta)->equals($meta);
+  }
+
   function testItReencodesSerializedObjectToJsonEncoded() {
     $queue = $this->queue;
     $newsletter_rendered_body = $this->rendered_body;