ST_Boundary('LINESTRING EMPTY') returns random numbers

[strk]

# select ST_AsText(ST_Boundary('LINESTRING EMPTY'));
NOTICE:  lwgeom_api.c [138] called with n=0 and npoints=0
NOTICE:  lwgeom_api.c [138] called with n=-1 and npoints=0
                              st_astext                              
---------------------------------------------------------------------
 MULTIPOINT(9e-323 4.6729030886132e-310,9e-323 4.6729030886132e-310)
(1 row)

See also #4956 and ​https://gitlab.com/postgis/postgis/-/merge_requests/50 for testcases with this

[kalenikaliaksandr <kalenik.aliaksandr@…>]

In cce909b/git:

Fix ST_Boundary('LINESTRING EMPTY')

Closes #4960
Includes unit test

[Darafei Praliaskouski <me@…>]

In e35fbe1/git:

Merge and format lwgeom_boundary tests

Thanks Aliaksandr Kalenik and Sandro Santilli for the work on it.

Closes #4956
Closes #4960
Closes #4961
Closes ​https://github.com/postgis/postgis/pull/626