pgsql: Do not pass along strings with NUL characters in UTF-8.

lib/modules/Sql.pmod/pgsql_util.pmod

@@ -1195,6 +1195,10 @@ class sql_result {
               value = (string)value;
               switch (cenc) {
                 case UTF8CHARSET:
+                  if (has_value(value, 0))
+                    SUSERERROR("NUL characters not allowed in PG-UTF-8: %O\n",
+                     value);
+                  else
                     value = string_to_utf8(value);
                   break;
                 default: