ofxCV can't compile some examples of-0.9

both example-difference-columns and example-difference and some other give me this error and can’t
it show this error utilities.h
// allocation
// only happens when necessary
template inline void allocate(T& img, int width, int height, int cvType) {
if (!img.isAllocated() || //here it shows and error ?
getWidth(img) != width ||
getHeight(img) != height ||
getCvImageType(img) != cvType)
img.allocate(width, height, getOfImageType(cvType));

OF/of_v0.9.0_osx_release/addons/ofxCv/libs/ofxCv/include/ofxCv/Utilities.h:173:18: No member named ‘isAllocated’ in ‘ofVideoGrabber’

how to fix this?