LG-439 Don't raise error for invalid user params

[monfresh]

Why: There is a bug in Devise where if you visit the sign in page
with a user param set to a String, it will raise an exception. The
bug has been fixed and merged into master, but hasn't been released
to Rubygems yet. We could either point our gem to Devise's master
branch, or temporarily add some code to prevent the bug until the fix
is released. I opted for the latter because I don't know how stable the
master branch is and what kind of changes are in it.

Hi! Before submitting your PR for review, and/or before merging it, please
go through the following checklist:

• For DB changes, check for missing indexes, check to see if the changes
  affect other apps (such as the dashboard), make sure the DB columns in the
  various environments are properly populated, coordinate with devops, plan
  migrations in separate steps.

• For route changes, make sure GET requests don't change state or result in
  destructive behavior. GET requests should only result in information being
  read, not written.

• For encryption changes, make sure it is compatible with data that was
  encrypted with the old code.

• For secrets changes, make sure to update the S3 secrets bucket with the
  new configs in all environments.

• Do not disable Rubocop or Reek offenses unless you are absolutely sure
  they are false positives. If you're not sure how to fix the offense, please
  ask a teammate.

• When reading data, write tests for nil values, empty strings,
  and invalid formats.

• When calling redirect_to in a controller, use _url, not _path.

• When adding user data to the session, use the user_session helper
  instead of the session helper so the data does not persist beyond the user's
  session.

• When adding a new controller that requires the user to be fully
  authenticated, make sure to add before_action :confirm_two_factor_authenticated.

[mryenq]

LGTM (unless you want to perform the necessary gymnastics to satisfy Reek).

Do you want to add a comment for revisitation if/when we update Devise?

[monfresh]

I will add an issue in JIRA to make sure we remove this code when we update Devise.