Symfony version(s) affected: 4.2

Description
Given a class implementing \Serializable, if the serialize is called on a badly constructed instance and throws a \TypeError, then the Registry::getClassReflector failed because of https://github.com/symfony/symfony/blob/master/src/Symfony/Component/VarExporter/Internal/Registry.php#L101 .

How to reproduce

class Foo implements \Serializable
{
  $foo;
  public function __construct(string $foo) {$this->foo = $foo;}

  public function getFoo(): string {return $this->foo;} // throws a TypeError if $this->foo is null
  
  public function serialize(): string { return [$this->getFoo()]; }

  public function unserialize(string $str): { [$this->foo] = \unserialize($str); }
}

Possible Solution

Note that catching \Throwable in https://github.com/symfony/symfony/blob/master/src/Symfony/Component/VarExporter/Internal/Registry.php#L105 could solve the issue, but would replace serialization by a PropertyAccess hydration which is much more slower