ext/pdo_odbc: Do not populate message if there is no driver error

[Girgias]

@NattyNarwhal do you have instructions on how to set a DB on Linux/Fedora?

I think the double warning is an existing bug in PDO anyway, but I'm still confused as to why it is printing NULL bytes here.

[NattyNarwhal]

For setting up SQL Server on Linux, I set up a VM or container running Ubuntu LTS (if you do that, use 22.04, 24.04 requires some work to make it run. The Docker container should also work as well.

[Girgias]

Okay, "no need" to set-up a VM, I figured out the issue by staring at PDO long enough.

Only issue is I'm not exactly sure how to handle the following build failure on Linux X64 NTS:

 /home/runner/work/php-src/php-src/ext/pdo_odbc/odbc_driver.c: In function ‘pdo_odbc_fetch_error_func’:
/home/runner/work/php-src/php-src/ext/pdo_odbc/odbc_driver.c:44:33: error: the comparison will always evaluate as ‘false’ for the address of ‘last_err_msg’ will never be NULL [-Werror=address]
   44 |         if (einfo->last_err_msg == NULL || strlen(einfo->last_err_msg) == 0) {
      |                                 ^~
In file included from /home/runner/work/php-src/php-src/ext/pdo_odbc/odbc_driver.c:29:
/home/runner/work/php-src/php-src/ext/pdo_odbc/php_pdo_odbc_int.h:116:14: note: ‘last_err_msg’ declared here
  116 |         char last_err_msg[SQL_MAX_MESSAGE_LENGTH];
      |              ^~~~~~~~~~~~

As it seems that last_err_msg is not always a fixed length array, any suggestions?

[NattyNarwhal]

I'm pretty sure last_err_msg should always be a fixed-length array in pdo_odbc_errorinfo, so the null check is redundant.