faces/clock: clear segments if not in 024h mode

faces/clock: clear segments if not in 024h mode

There was an issue where the clock's display would remain in 024h mode
even after switching back to 12h/24h mode because it only took into
account the leading zero bit, whose value is meaningless unless the
24h mode bit is also set.

The issue is fixed by taking both bits into account.

Closes #476.

Reported-by: CarpeNoctem <cryptomax@pm.me>
GitHub-Issue: https://github.com/joeycastillo/Sensor-Watch/issues/476