subtract_psf, used in BasicPSFPhotometry.nstar (and thus all classes based off this class) will fail with ValueError: Can't add array. Small array too large. if fitshape has shape equal in at least one length to data.shape.

This is due to subtract_psf using astropy.nddata.add_array if subshape is None evaluates false. add_array fails to check if sizes are greater than or equal; I plan to put in a pull request through astropy to fix this. However, for exactly equal fitshape and data shape if subshape is None could be amended to if subshape is None or np.all(i == j for i, j in zip(fitshape, data.shape)) or equivalent.