## Description 

- `mut` checks for locals did not consider if the local had not yet been
assigned, e.g. `let x; x = 0;`
- The checks are now done during the locals safety checks 

## Test Plan 

- Updated tests

---
If your changes are not user-facing and do not break anything, you can
skip the following section. Otherwise, please briefly describe what has
changed under the Release Notes section.

### Type of Change (Check all that apply)

- [ ] protocol change
- [X] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

Improved Move's reporting of unused variables. In some cases, errors
that were previously reported as unused assignments are now correctly
marked as unused variables.