Generated fragment-masking.ts is not compatible with noUncheckedIndexedAccess on upcoming RC

[2snEM6]

Which packages are impacted by your issue?

No response

Describe the bug

As I mentioned here: #9196 (comment) (#9196)

if an user has noUncheckedIndexedAccess set to true on their tsconfig, then fields might be undefined, causing type checking to fail.

Code is here: https://github.com/dotansimha/graphql-code-generator/pull/9196/files/7ad08f56be5ff8d0ee7c93250c5988cb3fed2ea4#diff-f6309550f61b610a24949b53525e396490f4af6dbcc264d82cb6bfd3ea9ea8a8R51

Your Example Website or App

https://github.com/dotansimha/graphql-code-generator/pull/9196/files/7ad08f56be5ff8d0ee7c93250c5988cb3fed2ea4#diff-f6309550f61b610a24949b53525e396490f4af6dbcc264d82cb6bfd3ea9ea8a8R51

Steps to Reproduce the Bug or Issue

1. Run type checking with tsconfig noUncheckedIndexedAccess on against Add @defer directive support #9196 (comment)
2. Watch TS complain about possible undefined index access for the fields variable

Expected behavior

fields variable should be checked for undefined/null values

Screenshots or Videos

No response

Platform

• OS: [e.g. macOS, Windows, Linux]
• NodeJS: [e.g. 18.5.0]
• graphql version: [e.g. 16.3.0]
• @graphql-codegen/* version(s): [e.g. 2.6.2]

Codegen Config File

No response

Additional context

No response

[beerose]

Fixed in #9385