[PATCH] EXC_BAD_ACCESS in SC_execute

Hello,

I am looking into dmp files which we collect when our application crashes.
Using google breakpad/stackwalking I am generating the stacktrace. The
crash looks like this:

Crash reason: EXC_BAD_ACCESS / 0x0000000d
Crash address: 0x0

Thread 10 (crashed)
0 psqlodbcw.so!SC_Execute + 0x10bd

I couldn't get the source line so I had to dig through the assembly.
I was able to determine the error is happening on line statement.c line
2191 (from the latest version in the repository).

numcols = QR_NumResultCols(tres);
(this expands to)
numcols = tres->fields->num_fields

The crash happens on the dereference of fields. It could be a null pointer,
I'm not sure because I can't reproduce the error.
Apparently EXC_BAD_ACCESS can be SIGSEGV or SIGBUS.
I have generated a patch to handle the null pointer case.