The electron wavelength is around 4 picometers at low energies. The wavelength also imposes a limit on the resolution of electron microscopy, for example. The wavelengths are really small, but they are not zero.
Sure, but when an electron hits a surface (like a detector), it doesn't hit it with a splotch of 4 picometer in size, it hits it as a dot (as far as one can measure, given the uncertainty principle)... right? Same as any photon.