This checks seems to be necessary because if the frames are calculated elsewhere in Matlab numFrames and startAt are generally integer numbers in "double" format. The original btkCropAcquisition function gives an error if index are not in integer format.
a fix to my wrong fix :-)

a fix to my wrong fix :-)
Added check on input variables
Merge pull request #5 from modenaxe/master

[FIX] These additional checks seems to be desirable because if the frames are calculated e...