The Ctrl+↑/↓ keyboard-nav useEffect sat AFTER `if (!range) return`, so on a band
with no range — e.g. a spurious 33 cm frequency briefly reported by an Icom over
CAT — the component returned before that hook and the hook count changed between
renders, crashing the whole window with React #300. Moved the effect above the
early return; lo/hi already fall back to [0,1] when there's no range.
rouggy
f0959c796d