web/admin: handle elements in slot=form not being forms

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

web/src/elements/buttons/ModalButton.ts

@@ -54,7 +54,9 @@ export class ModalButton extends LitElement {
 
     resetForms(): void {
         this.querySelectorAll<HTMLFormElement>("[slot=form]").forEach(form => {
-            form?.resetForm();
+            if ("resetForm" in form) {
+                form?.resetForm();
+            }
         });
     }