chore: warnings and notes cleanup for various files in /src/lib/mu

Build logs are littered with a couple warnings and notes that can be cleaned up. For example:

```warning: using the result of an assignment as a condition without parentheses ```
```warning: 'uint16' is deprecated```

Start by inspecting /src/lib/mu and reproducing the build to identify the warnings and notes mentioned in the issue, including assignment conditions and deprecated uint16 usage. Done means the relevant warnings and notes in that area are resolved and the build logs are clean.

Written by the indexing model from the issue text.