Weird form app file upload bug

Hi

I've spent a lovely Friday night trying to solve this error! I hope my solution, if it is one, helps someone else.

In the Form App perch:input file uploads with accept="[any mime type]" set on them will fail* (at least on my MAMP and production servers) if you set the order of apps in a form tag like this:

    <perch:form id="appointment" method="post" app="perch_forms perch_mailchimp" double-optin="true" send-welcome="true">

Swapping the apps over fixes the error.**

    <perch:form id="appointment" method="post" app="perch_mailchimp perch_forms" double-optin="true" send-welcome="true">

*The form submits but the page layout breaks

**Found this out via a combined effort of absolute desperation and total fluke.