A compiling warning in jsonb_populate_record_valid

[Richard Guo]

I came across a warning when building master (a044e61f1b) on old GCC
(4.8.5).

jsonfuncs.c: In function ‘jsonb_populate_record_valid’:
../../../../src/include/nodes/miscnodes.h:53:15: warning: the comparison
will always evaluate as ‘true’ for the address of ‘escontext’ will never be
NULL [-Waddress]
  ((escontext) != NULL && IsA(escontext, ErrorSaveContext) && \
               ^
jsonfuncs.c:2481:23: note: in expansion of macro ‘SOFT_ERROR_OCCURRED’
  return BoolGetDatum(!SOFT_ERROR_OCCURRED(&escontext));

This was introduced in commit 1edb3b491b, and can be observed on several
systems in the buildfarm too, such as:
https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=arowana&dt=2024-01-25%2004%3A54%3A38&stg=build

Thanks
Richard