Rules F841 cause autofix error

[qarmin]

Ruff 0.0.287 (latest changes from main branch)

ruff  *.py --select F841 --no-cache --fix

file content(at least simple cpython script shows that this is valid python file):

gitm_varnames = {'Argon Mixing Ratio': ['r_Ar', 'linear', ''],
                 'Electron Energy Flux': ['ElectronEnergyFlux', 'exponential',
                                           ''],
                 'Total Absolute EUV': ['TotalAbsoluteEUV', 'linear',
                                           'K per timestep'],
              'AltIntNOCooling (W/m2)': 'linear'}
def _read(varlist, attrs, newfile=True):
    '''
    '''
    if len(rawRecLen) < 4:
        var.append(unpack(endChar+'%is' % (recLen), f.read(recLen))[0])
    attrs['time'] = datetime(yy, mm, dd, hh, mn, ss, ms).replace(
        tzinfo=timezone.utc).isoformat(sep=' ')
    (oldLen) = unpack(endChar+'l', f.read(4))

error

/home/rafal/test/tmp_folder/6735003.py:14:6: F841 Local variable `oldLen` is assigned to but never used
Found 1 error.

error: Autofix introduced a syntax error. Reverting all changes.

This indicates a bug in `ruff`. If you could open an issue at:

    https://github.com/astral-sh/ruff/issues/new?title=%5BAutofix%20error%5D

...quoting the contents of `/home/rafal/test/tmp_folder/6735003.py`, the rule codes F841, along with the `pyproject.toml` settings and executed command, we'd be very appreciative!

python_compressed.zip