This radio was disabling tx when duplex='' (i.e. simplex) instead of
when duplex='off'

Fixes: 11511

The memory editor will fail with a 'KeyError: N' error if the user
attempts to paste more memories than will fit. This makes us not
choke, stop when we get to the end, and report to the user (unless
the memories that don't fit are empty).

Fixes #11510