issue #2118: fix undefined method for nil:NilClass exception

app/workers/post_receive.rb

@@ -7,8 +7,8 @@ class PostReceive
 
     # Ignore push from non-gitlab users
     user = if identifier.eql? Gitlab.config.gitolite_admin_key 
-      email = project.commit(newrev).author.email
-      User.find_by_email(email)
+      email = project.commit(newrev).author.email rescue nil
+      User.find_by_email(email) if email
     elsif /^[A-Z0-9._%a-z\-]+@(?:[A-Z0-9a-z\-]+\.)+[A-Za-z]{2,4}$/.match(identifier)
       User.find_by_email(identifier)
     else