Fixed undefined behaviour in color space correction filter.
Fixed undefined behaviour in color space correction filter.

svn path=/trunk/libavg/; revision=7093

scotty007/libavg,libavg/libavg,hoodie/libavg,th3infinity/libavg,yyd01245/libavg,scotty007/libavg,scotty007/libavg,hoodie/libavg,scotty007/libavg,libavg/libavg,th3infinity/libavg,yyd01245/libavg,yyd01245/libavg,libavg/libavg,libavg/libavg,hoodie/libavg,yyd01245/libavg,th3infinity/libavg,hoodie/libavg,th3infinity/libavg