web: fix t.reset is not a function

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

web/src/elements/buttons/ModalButton.ts

@@ -55,7 +55,7 @@ export class ModalButton extends LitElement {
 
     resetForms(): void {
         this.querySelectorAll<HTMLFormElement>("[slot=form]").forEach(form => {
-            form.reset();
+            form?.reset();
         });
     }