Classic Editor mode: Clicking on the pattern list sometimes breaks editing

[GoogleCodeExporter]

Can't reproduce it easily, but often when you have a longer song when you click 
on the pattern list, the red square is off by a few pixels, sometimes a full 
line. (Never more than a full line, and always above the line you meant to 
select, never below.)

In that "mode", editing the pattern number doesn't work (nothing seems to 
happen) but your patterns become shifted up, sometimes KT even crashes. Note 
that I always (up to now at least) use a STEP of 0x40 and a LEN and LOOP in 
increments of STEP. (Which is mostly because of issue 108 about LEN != 0x40 
being off, as described in issue 108.)

Original issue reported on code.google.com by [email protected] on 17 Aug 2014 at 2:27