Don't unnecessarily invoke type loader when printing schema

[mfn]

Summary

Before #1303 , the type loader was not invoked when printing the schema and not mutation or subscription is defined.

This brings back the previous behaviour in this regard.

I'm not sure what is really wanted here, it was discovered as feedback in the preparation for graphql-laravel for the graphql-php v15 upgrade in rebing/graphql-laravel#953 (comment) and we added a test case which did not trigger the typeloader in v14 ( rebing/graphql-laravel#995 , though at that point it wasn't yet clear what's going on).

It's not a big issue, but I figured I open the PR as discussion, if we really need to invoke the type loader if we already see that there's not such top level type defined.

The test is just quickly put together: if you change back to the code in master, the test throws an exception.

Let me know what you think, cheers.

[mfn]

Should have run the full test suite locally before I guess 😅

I see what it breaks, though not sure why with my change. But I guess that's a reason to no go forward with this PR.

[spawnia]

The type loader should not throw when a type is not found. Such behaviour would be problematic because types can be requested by the client, e.g. in a fragment spread.

[mfn]

Thanks!

I wasn't aware of this, the exception in graphql-laravel predates my involvement by a couple of years and was added in the original fork before I even knew what GraphQL was 😅.

I'm closing this PR as I'm sure this is just unnecessary noise and I'll consider your advice, thank you 🙏🏼