[html-formfu] _save_multi_value_fields_many_to_many fails if condition_from_stash set?

[Alex Povolotsky]

Hello!

Working with trivial many-to-many checkbox selection, I've triggered an 
error.

If, and only if condition_from_stash is set,  
_save_multi_value_fields_many_to_many for some reason fails to clean 
relationship before adding (double checked, it's c_f_s-related).

I've kludged it for now by adding forced clear of relationship before

$c->stash->{form}->model->update( $c->stash->{object} );

but I'd like to make it working without black magic.

Alex