Do not try to create verified mail for empty mail

Issue #1086
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/accounts/models.py

@@ -849,7 +849,7 @@ def post_login_handler(sender, request, user, **kwargs):
     profile = Profile.objects.get_or_create(user=user)[0]
 
     # Migrate django-registration based verification to python-social-auth
-    if (user.has_usable_password() and
+    if (user.has_usable_password() and user.email and
             not user.social_auth.filter(provider='email').exists()):
         social = user.social_auth.create(
             provider='email',