Fix crash when computing statistics with IM backend
Fix crash when computing statistics with IM backend

GetImageChannelStatistics returns ChannelStatistics *, not
ChannelStatistics **.

zuriu/magick,rainycape/magick,zuriu/magick,zuriu/magick,rainycape/magick,500px/magick,500px/magick,etix/magick,etix/magick,500px/magick,rainycape/magick,etix/magick