Don't delete username of DB after 24 hours

Pre-condition:

1. Open the main page forum
2. Select English language
3. Click on Sing Up
4. Input: username (not existing in the DB);
   Email (valid and no existing in the DB);
   Password/confirm password (for example: pass123);
   captcha the same as on image.

Steps:

1. Click Sing Up
2. Don't transition on link's from email.
3. Change systm time on computer on 24 hours.
4. Repeat pre-condition steps 1 - 4

Actual result: Error message are shown under the field: "User with this username already exists"

Expected result: Pop-up dialog with "" message is shown: you can finf activation mail on you email on you email box.