ps_symbols.ps procuded using gnuplot-5.5 is invalid

[Tatsuro M. <tma...@ya...>]

I cannot judge whether this is a bug or not.
The file ps_symbols.ps which is generated from ps_symbols.gpi is invalid using gnuplot-5.5.

$ gs ps_symbols.ps
GPL Ghostscript 9.55.0 (2021-09-27)
Copyright (C) 2021 Artifex Software, Inc.  All rights reserved.
This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY:
see the file COPYING for details.
Loading NimbusSans-Regular font from /usr/share/ghostscript/9.55.0/Resource/Font/NimbusSans-Regular... 4410900 2897778 3914624 2616235 1 done.
Error: /undefined in UL
Operand stack:
   1.0
Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   false   1   %stopped_push   1990   1   3   %oparray_pop   1989   1   3   %oparray_pop   1977   1   3   %oparray_pop   1833   1   3   %oparray_pop   --nostringval--   %errorexec_pop   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--
Dictionary stack:
   --dict:761/1123(ro)(G)--   --dict:0/20(G)--   --dict:81/200(L)--   --dict:51/256(L)--
Current allocation mode is local
Current file position is 19030
GPL Ghostscript 9.55.0: Unrecoverable error, exit code 1

ps_symbols.ps which is generated from ps_symbols.gpi is valid using gnuplot-5.4.4.

$ gs ps_symbols.ps
GPL Ghostscript 9.55.0 (2021-09-27)
Copyright (C) 2021 Artifex Software, Inc.  All rights reserved.
This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY:
see the file COPYING for details.
Loading StandardSymbolsPS font from /usr/share/ghostscript/9.55.0/Resource/Font/StandardSymbolsPS... 4377556 2802346 4217624 2918412 1 done.
Loading NimbusSans-Regular font from /usr/share/ghostscript/9.55.0/Resource/Font/NimbusSans-Regular... 4427860 2963335 4278224 2968221 1 done.
Loading NimbusMonoPS-Regular font from /usr/share/ghostscript/9.55.0/Resource/Font/NimbusMonoPS-Regular... 4554572 3182512 4338824 3002934 1 done.
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Tatsuro