Fix confusing crash when an unknown filter name is passed to optional/required

Changes

@@ -1,5 +1,8 @@
 
 9.50  UNRELEASED
+  - Fixed Mojolicious::Validator::Validation to croak with a clear message naming the filter when an unknown
+    filter name is passed to "optional" or "required", instead of crashing with a confusing
+    "Can't locate object method """ error.
 
 9.49  2026-08-10
   - Added EXPERIMENTAL support for partitioned cookies. (rawleyfowler)

lib/Mojolicious/Validator/Validation.pm

@@ -71,7 +71,9 @@ sub optional {
   return $self->topic($name) unless defined(my $input = $self->input->{$name});
 
   my @input = ref $input eq 'ARRAY' ? @$input : ($input);
-  for my $cb (map { $self->validator->filters->{$_} } @filters) {
+  for my $filter (@filters) {
+    my $cb = $self->validator->filters->{$filter};
+    Carp::croak qq{Unknown filter "$filter"} unless defined $cb;
     @input = map { $self->$cb($name, $_) } @input;
   }
   $self->output->{$name} = @input > 1 ? \@input : $input[0] if @input && !grep { !defined } @input;

t/mojolicious/validation_lite_app.t

@@ -279,6 +279,12 @@ subtest 'Custom filter' => sub {
   is_deeply $v->output, {foo => ['foo="bar"', 'foo="baz"']}, 'right result';
 };
 
+subtest 'Unknown filter' => sub {
+  my $v = $t->app->validation->input({foo => 'bar'});
+  eval { $v->optional('foo', 'does_not_exist') };
+  like $@, qr/Unknown filter "does_not_exist"/, 'clear error naming the unknown filter';
+};
+
 subtest 'Multiple empty values' => sub {
   my $v = $t->app->validation;
   ok !$v->has_data, 'no data';