Do not add attributes to push when none are passed (munir131#5)

Fixes munir131#4

Author: goodevilgenius

src/PubSubQueue.php

@@ -80,10 +80,13 @@ public function pushRaw($payload, $queue = null, array $options = [])
 
         $this->subscribeToTopic($topic);
 
-        return $topic->publish([
-            'data' => $payload,
-            'attributes' => $options,
-        ]);
+        $publish = ['data' => $payload];
+
+        if (! empty($options)) {
+            $publish['attributes'] = $options;
+        }
+
+        return $topic->publish($publish);
     }
 
     /**