fix(form): reset submitting flag when validation fails to keep dirtycheck

When the preventLeaving feature is used, the dirtycheck was ignored on a submit even when the validation failed (which aborts the submit).
Whenever a validation failes it should therefore also reset a possible existing submitting flag to keep the preventLeavin feature working

Author: lubber-de

src/definitions/behaviors/form.js

@@ -1192,6 +1192,7 @@ $.fn.form = function(parameters) {
             }
             else {
               module.debug('Form has errors');
+              submitting = false;
               module.set.error();
               if(!settings.inline) {
                 module.add.errors(formErrors);