feat: update mustget behavior

pkg/iterator/iterator.go

@@ -43,12 +43,12 @@ func (i Iterator[T]) Get() (T, error) {
 
 // MustGet is a version of Get, that panics if the datum cannot be returned.
 func (i Iterator[T]) MustGet() T {
-	var null T
-	if i.Done() {
-		return null
+	t, err := i.Get()
+	if err != nil {
+		panic(fmt.Errorf("cannot get current token: %w", err))
 	}
 
-	return i.items[i.index]
+	return t
 }
 
 // Forward increments the iterator if the iterator is not yet at the end of the