fix deprecation warning

Author: dlegland

ImageM/+imagem/+actions/+analyze/MeasureWithinSelection.m

@@ -60,7 +60,7 @@ function run(obj, frame)
         end
 
         % compute mean values within ROI for each channel
-        nc = channelNumber(img);
+        nc = channelCount(img);
         meanValues = zeros(1, nc);
         for i = 1:nc
             ch = channel(img, i);