Fails Silently Upon Invalid Email

[bcsam]

Description: If a user tries to sign up for nb with an invalid email address, the system detects it and does not allow the user to sign up but doesn't report anything to the user.

Reproduction Steps:

1. Navigate to the account creation page
2. Fill in all the fields but do not include an ending tag for the email (e.g. don't include @mit.edu)
3. Click sign up

Expected Behavior:
An error message appears such as: "Invalid email address. Try again!"

Actual Behavior:
The sign up button remains selected but no action occurs