Sessions/Speakers: Call for speakers - private link does not work

[hpdang]

Describe the bug
When enable a call for speakers and set it as private, the private link does not work https://eventyay.com/e/ae73f280/cfs/86c7b3df-f604-4359-a182-52e5d2192ae0

To Reproduce
Steps to reproduce the behaviour:

1. Go to 'Sessions & Speakers', enable Call for Speakers and select private option
   

2. A private link showed an error
   

Desktop

• OS: Ubuntu 18.04
• Browser: Chrome