Fortigate cannot detect Tor Browser

HI,

We have a Fortigate firewall that run firmware V7.2.4

we noticed some users are using Tor Browser to access some blocked sites by the firewall 

the firewall cannot detect it although application control is enabled and it is being blocked by it

however, when we checked the forward traffic log we found it under entries for HTTPS application with no result

but it is allowed

is there any way to detect and block this traffic

Thanks