requireResolversToMatchSchema: 'warn' throws an error

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Issue workflow progress

Progress of the issue based on the Contributor Workflow

• [ ] 1. The issue provides a reproduction available on Github, Stackblitz or CodeSandbox

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• [ ] 2. A failing test has been provided
• [ ] 3. A local solution has been provided
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Describe the bug

Currently when I use requireResolversToMatchSchema: 'warn' in makeExecutableSchema, an error is thrown.

To Reproduce Steps to reproduce the behavior:

See failing test in https://github.com/ardatan/graphql-tools/pull/5775.

Expected behavior

makeExecutableSchema should run and output warnings.

Environment:

• OS:
• @graphql-tools/schema:
• NodeJS: 20.9

Additional context