Prevent SIGSEGV in apply_error_callback when record was not decoded (#5703)

## Problem

See 

https://neondb.slack.com/archives/C036U0GRMRB/p1698652221399419?thread_ts=1698438997.903919&cid=C036U0GRMRB

## Summary of changes

Check if record pointer is not NULL before trying to print record
descriptor

## Checklist before requesting a review

- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.

## Checklist before merging

- [ ] Do not forget to reformat commit message to not include the above
checklist

Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>

pgxn/neon_walredo/walredoproc.c

@@ -895,7 +895,12 @@ apply_error_callback(void *arg)
 	StringInfoData buf;
 
 	initStringInfo(&buf);
-	xlog_outdesc(&buf, record);
+#if PG_VERSION_NUM >= 150000
+	if (record->record)
+#else
+	if (record->decoded_record)
+#endif
+		xlog_outdesc(&buf, record);
 
 	/* translator: %s is a WAL record description */
 	errcontext("WAL redo at %X/%X for %s",