[Investigate] Null exception in GetAxis method from Input.cs

When playing in editor with AltTester open, checking **Custom Input** throws error in console -> "Value cannot be null"

### Additional info

This issue was encountered in a client project, while upgrading from AltUnityTester 1.7.0 to AltTester Unity SDK 1.8.2.

Solution:
1. Comment instructions for _useCustomInput is true from GetAxis method.

2. Remove these 2 files: `AltTesterInputAxisData.json` & `AltTesterInputAxisData.json.meta`