Fixed key-up events firing key-down hotkeys which were filtered out.

For instance, if `f::` and `f up::` both exist and f is filtered out
due to Shift being pressed, releasing Shift before f would cause both
hotkeys to fire.  This "fire both on release" behaviour was introduced
by commit aba90cec, and was intended to apply only to prefix keys of
custom combinations.
v1.1.14.02