web/admin: fix error when copying token while none exist

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

web/src/elements/buttons/TokenCopyButton.ts

@@ -29,8 +29,8 @@ export class TokenCopyButton extends ActionButton {
                     this.buttonClass = PRIMARY_CLASS;
                 }, 1500);
             });
-        }).catch((err: Response) => {
-            return err.json().then(errResp => {
+        }).catch((err: Response | undefined) => {
+            return err?.json().then(errResp => {
                 throw new Error(errResp["detail"]);
             });
         });