Improved error messages when getting an absent field from fieldArgs

### Summary

Getting an incorrect field from a mutation FieldArgs results in a `unable to get type from undefined` error.

### Steps to reproduce

Try and get an absent field from a FieldArgs

### Expected results

More verbose error message clearly indicating that you're trying to get a field that doesn't exist.

### Actual results

Getting a can't read type from undefined error.

### Additional context

### Possible Solution