php_odbc_fetch_hash() Fixed a segfault when fetching certain SQL NULLs

php_odbc.c:1774 Changed the conditional to include the check:

	 && Z_TYPE_P(tmp) == IS_STRING

This avoids a potential segfault on 1775 where ZSTR_ macros are used
when the ZVAL is sometimes NULL.

Author: BRANDON KIRSCH

ext/odbc/php_odbc.c

@@ -1771,7 +1771,7 @@ static void php_odbc_fetch_hash(INTERNAL_FUNCTION_PARAMETERS, int result_type)
 		if (result_type & ODBC_NUM) {
 			zend_hash_index_update(Z_ARRVAL_P(return_value), i, &tmp, sizeof(zval *), NULL);
 		} else {
-			if (!*(result->values[i].name) && Z_TYPE_P(tmp) != IS_NULL) {
+			if (!*(result->values[i].name) && Z_TYPE_P(tmp) == IS_STRING) {
 				zend_hash_update(Z_ARRVAL_P(return_value), Z_STRVAL_P(tmp),	Z_STRLEN_P(tmp)+1, &tmp, sizeof(zval *), NULL);
 			} else {
 				zend_hash_update(Z_ARRVAL_P(return_value), result->values[i].name, strlen(result->values[i].name)+1, &tmp, sizeof(zval *), NULL);