ATL08 PhoREAL Absolute Canopy Heights Returns 0's

Using the "phoreal" parameter set to access the atl08 API, when setting "use_abs_h" to 'True' the canopy heights that are returned are 0. When "use_abs_h" is set to 'False' the value are output as normal.

The following querry when will replicate the error:

parms = {
    "poly": sliderule.toregion('bounding_box.geojson')['poly'],
    "t0": '2021-01-01T00:00:00Z',
    "t1": '2021-04-30T00:00:00Z',
    "srt": icesat2.SRT_LAND,
    "len": 12,
    "res": 12,
    "pass_invalid": True, 
    "atl08_class": ["atl08_ground", "atl08_canopy", "atl08_top_of_canopy"],
    "phoreal": {"binsize": 1.0, "geoloc": "mean", "use_abs_h": True, "send_waveform": False}
}

atl08 = icesat2.atl08p(parms, keep_id=True)

With the bounding_box.geojson located here: https://utexas.box.com/s/ubrpaxyv3h2q0jiowy4nsgoxauhakq1e

SlideRuleEarth / sliderule

ATL08 PhoREAL Absolute Canopy Heights Returns 0's #387