This error occurs due to your corrupted Profile Image. You may know it is corrupted if there is no image at the top-right corner of the screen, right beside your name. If everything is fine, it should show either your uploaded profile image or the placeholder image: 
To update your Profile Image, please refer to: Update User Profile
Once the Profile Image shows up correctly, you should be able to continue your registration smoothly.
If this error still occurs, please contact the centre and provide them with the following information:
Your Name
Exam Intake Name
Candidate Number