check contentlanguages not null on getter (#14891)

Co-authored-by: Cameron Jenkins <cameron.jenkins@torqit.ca>

models/User.php

@@ -588,7 +588,7 @@ public function getImage($width = null, $height = null)
      */
     public function getContentLanguages()
     {
-        if (strlen($this->contentLanguages)) {
+        if (is_string($this->contentLanguages) && strlen($this->contentLanguages)) {
             return explode(',', $this->contentLanguages);
         }