#507: fix array widget error handling

This fixes #507.

To test this, introduce errors in the `demo/rose-config-edit/demo_meta/app/01-types` app `many types` page - in particular, for the variables `my_char_array` and `my_real_array`. 

`my_real_array` errors can be introduced trivially by breaking the real number requirement, and deleting quotes with metadata off will work for `my_char_array`.

@matthewrmshin, please review.