FIX: Missing timezone guess on email session login (#9404)

Timezone is guessed by moment.js if unset upon a normal login, but was not when
logging in via an email link. This adds logic to update a guessed
timezone upon email login so timezones don't end up blank.

app/controllers/session_controller.rb

@@ -368,6 +368,7 @@ class SessionController < ApplicationController
       elsif payload = login_error_check(user)
         return render json: payload
       else
+        user.update_timezone_if_missing(params[:timezone])
         log_on_user(user)
         return render json: success_json
       end