Improve Ctrl + F behavior after CmdFindMatch

[kjk]

Doing Ctrl + F (CmdFindFirst) we unconditionally copy selection to edit search.

We used to only copy when edit was empty.

However, now the sequence:

• change search case-sensitivity (CmdFindMatch) from no-match-case to match-case
• Ctrl + F

Now we copy the selection from no-match-case to text box, which is not great behavior.

But don't want to revert to previous behavior either.

Would need some smarter logic but not sure what.