Swallowed error if add files field to spin.toml

[kate-goldenring]

Adding a files field to the spin.toml causes the application to error even if i am not using them.

Reproduce

Create a simple hello world app, create a mydir directory, and add the following files field to the application manifest files = [{ source="mydir", destination="/" }]:

spin new -t http-rust files-bug --accept-defaults
 cd files-bug
mkdir mydir
# add `files = [{ source="mydir", destination="/" }]` to component
spin build --up

When you curl the app you get curl: (52) Empty reply from server with no error logged

[k0pernicus]

Note: I get that error yesterday too (I forgot to create an issue).

It seems that the issue is because the folder is empty.
As an example, if you create a file / directory in it and the error will disappear.

I did not check the code to know the exact reason yet.