Setting form['#attributes'] as an array breaks other modules' attributes

Upload module's form_alter currently resets form attributes wholesale:

$form['#attributes'] = array('enctype'] => 'multipart/form-data');

This breaks other modules as any attributes, e.g. a class they might have set are overwritten.

Instead in form_alter hooks we need to set just the key in question. In this case:

$form['#attributes']['enctype'] = 'multipart/form-data';