Unconditional do_probe_raise() in probe_pt()

[AnHardt]

If Z_RAISE_BETWEEN_PROBINGS is null or undefined the probe is currently not raised by home_offset[Z_AXIS] and zprobe_zoffset. But when the smallest bit different from 0 it is.

If an undefined Z_RAISE_BETWEEN_PROBINGS expands to 0 (and it does) this is the solution.

A similar asymmetry exists with the newly introduced 'short-cut' in G28 - but it's the rise before anything is probed - so should not make a difference.

This asymmetry likely causes the effects in #4177

[thinkyhead]

@AnHardt This may only be covering up a bug, I think. For one thing we do not want anything "raised by home_offset[Z_AXIS] and zprobe_zoffset." The zero point for Z is not 0.0, but home_offset[Z_AXIS]. So whenever the probe hits the bed, the current_position[Z_AXIS] (for the nozzle) is supposed to be set to home_offset[Z_AXIS] - zprobe_zoffset. Then if we raise the nozzle by Z_RAISE_BETWEEN_PROBINGS it only moves up by that amount, to home_offset[Z_AXIS] - negative_zprobe_zoffset + Z_RAISE_BETWEEN_PROBINGS.

Is this already considered here?

I can see that skipping the raise would be a problem for a positive zprobe_zoffset (where the nozzle is the probe) because we need to raise to at least 0.0 just to get the nozzle off the bed.