The username cannot contain multiple spaces in a row.

We tried to use civicrm entity module with rules to create drupal user on civicrm contact creation. In civicrm_entity.module file, the display name is used in the name field of drupal user creation which fails if the user enters last name as "Test - Test" with two spaces it shows this error message after creating the membership - "The username cannot contain multiple spaces in a row". This doesn't happen if the last name contain only one space like "T Test". Please advice how to handle this issue, thanks. Below is an attached file for the error message.