Fix a breathing error during centers trade.
sdr> heads lead right
| 4B>  3G<  1B>  2G<
| 
| 4G>  3B<  1G>  2B<
sdr> touch; fan the top
| 3B^  4Gv  3G^  4Bv  2B^  1Gv  2G^  1Bv
sdr> cast off 3/4
| 4G>  4B>  1G>  1B>
| 
| 3B<  3G<  2B<  2G<
sdr> centers trade
| 4G>  3G>  2B>  1B>
| 
| 3B<  4B<  1G<  2G<
sdr> /exit