- Replace `Default::default()` with `std::ptr::null_mut()` or `std::ptr::null()` for FFI calls - Change `WideCStr::from_ptr` to `WideStr::from_ptr` for better safety - Remove redundant error variants in `LoadStrRcError` and `ExpandEnvVarError` - Reorder imports for better readability - Add test cases for `StrRc` and `ExpandString` utilities - Improve documentation comments for icon loading functions