Missing namespace for LogicException in Address::create

Problem/Motivation

Address::create attempts to throw a PHP LogicException if it doesn't recognize the content of the $address param.

Steps to reproduce

Call Address::create(null);.

Observe that the following error is generated:

Notice: Undefined variable: result in Drupal\symfony_mailer\Address::convert();

Proposed resolution

Prefix LogicException with a backslash in order to reference the correct namespace.