bugfix - added extra conditional statement checking for the presence of chanpos

git-svn-id: svn+ssh://svn.fcdonders.nl/home/svnroot/fieldtrip/trunk@8579 0cf7c7f0-3615-4144-b4e6-68da3bce3cd0
automatically synchronized identical files to revision 8579

git-svn-id: svn+ssh://svn.fcdonders.nl/home/svnroot/fieldtrip/trunk@8580 0cf7c7f0-3615-4144-b4e6-68da3bce3cd0