Add guard for custom module provider lookup in TMManager (#49738)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49738

**Context**

- D70012142 added TM module provider support
- This was causing RN MacOS to silently fail to load any platform modules since it didn't implement the delegate method

Changelog:
[iOS][Fixed] - Add guard for custom module provider lookup in TMManager

Reviewed By: sbuggay

Differential Revision: D70357542

fbshipit-source-id: 5b338616655ecb84cdb3c60e243fdb99444af657