Validation fails if query arg is a list with null items

[papermana]

Describe the Bug
If validation is on, and I make a query where one of the arguments is a list containing at least one null, then the query will fail with a message "validationErrors: TypeError: Cannot read properties of null (reading 'constructor')".

To Reproduce
Have a query like:

myQuery(@Arg('inputs', () => [Foo], { nullable: 'items' }) inputs: Array<Foo | null>) {
  // ...
}

Then, perform a query like

query Foo {
 myQuery(inputs: [null])
}

Expected Behavior
There should be no validation error.

Logs

ArgumentValidationError: Argument Validation Error
    at Object.validateArg (/Users/dominik/projects/snipped/node_modules/type-graphql/dist/resolvers/validate-arg.js:29:15)
    at async Promise.all (index 1)
    at async Promise.all (index 0) {
  validationErrors: TypeError: Cannot read properties of null (reading 'constructor')
      at ValidationExecutor.execute (/Users/dominik/projects/snipped/node_modules/src/validation/ValidationExecutor.ts:57:14)
      at Validator.coreValidate (/Users/dominik/projects/snipped/node_modules/src/validation/Validator.ts:107:14)
      at Validator.validateOrReject (/Users/dominik/projects/snipped/node_modules/src/validation/Validator.ts:53:31)
      at validateOrReject (/Users/dominik/projects/snipped/node_modules/src/index.ts:91:40)
      at /Users/dominik/projects/snipped/node_modules/type-graphql/dist/resolvers/validate-arg.js:21:55
      at Array.map (<anonymous>)
      at Object.validateArg (/Users/dominik/projects/snipped/node_modules/type-graphql/dist/resolvers/validate-arg.js:21:40)
      at async Promise.all (index 1)
      at async Promise.all (index 0)
}

Environment (please complete the following information):

• OS: macOS 12.2.1
• Node 16.14.0
• Package version 1.0.0-rc.1, but tested 1.1.1 as well
• TypeScript version 4.5.4

Additional Context
n/a