Fix mentions

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

js/src/types/actor/actor.model.ts

@@ -52,9 +52,7 @@ export class Actor implements IActor {
   }
 
   public displayName(): string {
-    return this.name != null && this.name !== ""
-      ? this.name
-      : this.usernameWithDomain();
+    return displayName(this);
   }
 }
 
@@ -68,6 +66,12 @@ export function usernameWithDomain(actor: IActor, force = false): string {
   return actor.preferredUsername;
 }
 
+export function displayName(actor: IActor): string {
+  return actor.name != null && actor.name !== ""
+    ? actor.name
+    : usernameWithDomain(actor);
+}
+
 export function displayNameAndUsername(actor: IActor): string {
   if (actor.name) {
     return `${actor.name} (@${usernameWithDomain(actor)})`;