Is this still a problem in git master? Normally these sort of errors are rather easy to fix but looking at this particular code, I cannot fathom why it'd fail. UserSystemGifts' constructor intentionally accepts both strings (user names) as well as full User objects; assuming a string is provided, User::newFromName() is called on it to turn it into a User object. There is some potential for failure here as the code does not ensure that the aformentioned call to User::newFromName() indeed returns a valid User object, but provided that you're logged in and all, I think it's safe to say your user name is valid at that point.

public function __construct( $user ) {
  if ( $user instanceof User ) {
    $this->user = $user;
  } else {
    $this->user = User::newFromName( $user );
  }
    $this->user_id = $user->getId();
    $this->user_name = $user->getName();
    $this->actorId = $user->getActorId();
  }

If a string is provided as the constructor argument, then throughout this block scope $user variable is of string type, it'll never change to object.

You're only changing the object property $user which is different from the $user variable passed in the constructor.

You need to change all these get* calls to be on the property $this-user->get and not on the potential string variable $user->get.

Alternatively you can also change the else statement to ensure the object is also assigned to a new $user variable (in addition to the $user property), so you can safely do a method call on it and remove the need for altering the get* calls.

$this->user = $user = User::newFromName( $user );

Change 629638 had a related patch set uploaded (by Jack Phoenix; owner: Jack Phoenix):
[mediawiki/extensions/SocialProfile@master] Use the correct variable to prevent fatals

https://gerrit.wikimedia.org/r/629638

Change 629638 merged by jenkins-bot:
[mediawiki/extensions/SocialProfile@master] Use the correct variable to prevent fatals

https://gerrit.wikimedia.org/r/629638