Mixed version error from Joi.isSchema() for validation params set to "false" (nothing allowed).

[Invader444]

Issue

Hapi 20 uses @hapi/validate internally, and for validation options set to false, it will use this as the schema:
Validator.object({}).allow(null)

Of course, its internal version will not match Joi's, and so we have a mixed version error from Joi.isSchema().

E.g.

response: {
  schema: false
}

Environment

npx envinfo --npmPackages '*hapi*' --binaries

Binaries:
Node: 14.16.1 - ~/.nvm/versions/node/v14.16.1/bin/node
npm: 6.14.12 - ~/.nvm/versions/node/v14.16.1/bin/npm
npmPackages:
hapi-swagger: ^14.5.1 => 14.5.1

Steps to Reproduce

Example route:

{
  method: 'GET',
  path: '/global',
  handler: (request, h) => {
    return null;
  },
  options: {
    tags: ['api'],
    response: {
      schema: false
    }
  }
}

Expected Behavior

The swagger documentation is generated normally.

Actual Behavior

This error is thrown when fetching swagger.json:

Error: Cannot mix different versions of joi schemas
    at new module.exports (~/[redacted]/node_modules/@hapi/hoek/lib/error.js:23:19)
    at module.exports (~/[redacted]/node_modules/@hapi/hoek/lib/assert.js:20:11)
    at Object.exports.isSchema (~/[redacted]/node_modules/joi/lib/common.js:132:5)
    at Object.utilities.isJoi (~/[redacted]/node_modules/hapi-swagger/lib/utilities.js:249:24)
    at module.exports.internals.properties.internals.properties.parseProperty (~/[redacted]/debugServer/node_modules/hapi-swagger/lib/properties.js:67:18)
    at module.exports.internals.responses.internals.responses.getResponse (~/[redacted]/node_modules/hapi-swagger/lib/responses.js:142:41)
    at module.exports.internals.responses.internals.responses.build (~/[redacted]/node_modules/hapi-swagger/lib/responses.js:52:29)
    at ~/[redacted]/node_modules/hapi-swagger/lib/paths.js:311:36
    at Array.forEach (<anonymous>)
    at module.exports.internals.paths.internals.paths.buildRoutes (~/[redacted]/node_modules/hapi-swagger/lib/paths.js:164:10)

[Invader444]

Not really sure what the optimal solution is here. Could maybe catch this error and try Validator.isSchema in the catch?

Then again, Validator shouldn't be used directly by anything outside Hapi internals...

[Invader444]

The workaround is to explicitly set these to Joi.object({}).allow(null) so they use Joi (which is what Hapi 19 would generate) instead of false, but that isn't ideal, especially since the Hapi docs recommend false for this purpose...

[robmcguinness]

Related hapijs/hapi#4246