[BUG] Possible occurrence of segfault in ecpg test

Hi,
The src/interfaces/ecpg/test/sql/bytea.pgc file contains the following code :
***
init();
exec sql truncate test;
exec sql insert into test values(:send_buf[0], :send_buf[1]);
exec sql insert into test values(:send_buf[0], :send_buf[1]);
exec sql select data1 into :recv_vlen_buf from test;
dump_binary(recv_vlen_buf[0].arr, recv_vlen_buf[0].len, 0);
dump_binary(recv_vlen_buf[1].arr, recv_vlen_buf[1].len, 0);
free(recv_vlen_buf);
***

recv_vlen_buf is initialized in the following way :
***
bytea recv_vlen_buf[][DATA_SIZE];
recv_vlen_buf = NULL
***

Thus, if the program behaves in an unexpected way and the transaction
is aborted before it executes the
"select data1 into :recv_vlen_buf from test" query, dump_binary will
refer to a null pointer. So, instead of an error
message, the user will see a segfault.

I think that in all such cases it is worth adding some checks into
.pgc and .c files (like in attached patch)

--
Best regards,
Daniil Davydov