messages: add option to show/hide linking on registration

In each of the Discord/Telegram/Matrix sections, the "Show on user
registration" option can be disabled to hide the "Link xxx" button on
the registration form. This is useful is you're only using these
registrations for admin purposes.

ts/modules/settings.ts

@@ -32,7 +32,7 @@ interface Setting {
 const splitDependant = (section: string, dep: string): string[] => {
     let parts = dep.split("|");
     if (parts.length == 1) {
-        parts = [section, parts[0]];
+        parts = [section, dep];
     }
     return parts
 };