Assig list slash command does not handle servers with no assignable roles

[BenSegal855]

Describe the bug
When a guild has no assignable roles, the assign list command simply loads forever. The issue comes from here as no message is actually sent when there are no assignable roles.

To Reproduce
-1 Run /assign list in a guild with no assignable roles (like the Steve Development guild)
-2 Observe bug

Expected behavior
The command should probably send the "There are no assignable roles in this server." message that the ubslassed command sends in cases like this.