Fix error on the sign up page for password requirements

What does this MR do and why?

• @JeremyWuuuuu started a discussion:

  I am experiencing this issue right now when the FF was not turned on, meaning that USER_INFO cannot be found within the ruleset, here this.findRule(USER_INFO) would be returning undefined back to checkValidity, which will cause error.

  

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Before	After

How to set up and validate locally

bin/rails c

Feature.disable(:display_password_requirements)

• Setup gdk to simulate SaaS - https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance and restart GDK.
• Make sure you have License locally (can be faked here by returning true).
• Sign out. Sign in as root. Visit /admin/application_settings/general.
• Enable all password requirements:

Click to expand

• Sign out. Visit /users/sign_up.
• Open browser console.
• Fill the first name with tttt.
• Make sure there is no error on reading type.

bin/rails c

Feature.enable(:display_password_requirements)

• Reload the page.
• Fill the form with valid data.
• Make sure you can submit the form.

Related to #509890 (closed)