[PostGIS] #5876: ST_AddPoint with empty point adds junk point

[PostGIS]

#5876: ST_AddPoint with empty point adds junk point
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  Reporter:  pramsey  |      Owner:  pramsey
      Type:  defect   |     Status:  new
  Priority:  medium   |  Milestone:  PostGIS 3.5.3
 Component:  postgis  |    Version:  master
Resolution:           |   Keywords:
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Comment (by pramsey):

 In general the `getPoint4d_p` function needs to `lwerror` out of all cases
 where it cannot successfully complete an access.
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5876#comment:1>
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