lazy copy bug with af::write<T> #2431

af::array left(0,0);
af::array right(2,1,2);
std::vector<float> d = { 1,1,2,2 };
right.write<float>(&d[0], sizeof(float) * 2 * 2);
left = right;
af_print(left);
d = { 10,10,20,20 };
right.write<float>(&d[0], sizeof(float) * 2 * 2);
af_print(left);