An array must be at least size of 1 for each axis, if only one of them is 0, then you can't store anything!
however, the array is 0 based, so the top-left-back position of a array will be (0,0,0), an array of size (3, 4, 5) will have (0 to 2, 0 to 3, 0 to 4), since from 0 to 2, you have 3 values (0 and 1 and 2), a 3x4x5 array can store 3x4x5 values (=60)
Due to the same logic, an array with a size of 0 on one axis cannot store any data, since you can store 0 values at the end (3x4x0 =0)