BUG #16268: SPI_getvalue requires IsTransactionState but TextDatumGetCString of SPI_getbinval - not!

The following bug has been logged on the website:

Bug reference:      16268
Logged by:          RekGRpth
Email address:      rekgrpth@gmail.com
PostgreSQL version: 12.2
Operating system:   Docker alpine edge
Description:

const char *data = SPI_getvalue(SPI_tuptable->vals[row],
SPI_tuptable->tupdesc, SPI_fnumber(SPI_tuptable->tupdesc, "data"));

raise TRAP: FailedAssertion("!(IsTransactionState())", File: "catcache.c",
Line: 1213)

but

const char *data = SPI_getvalue_my(SPI_tuptable->vals[row],
SPI_tuptable->tupdesc, SPI_fnumber(SPI_tuptable->tupdesc, "data"));

where

char *SPI_getvalue_my(HeapTuple tuple, TupleDesc tupdesc, int fnumber) {
    bool isnull;
    Datum datum = SPI_getbinval(tuple, tupdesc, fnumber, &isnull);
    if (isnull) return NULL;
    return TextDatumGetCString(datum);
}

works ok