v.external.out: Check for valid array before passing it to qsort (OSG…

…eo#4251)

Currently, if 'HAVE_OGR' macro is defined, as part of execution, we sort all formats by name using qsort. But, array containing all formats is assigned based on a conditional and if the conditional fails, it can be NULL.

Behavior of qsort when a NULL array is provided is undefined. To avoid getting into that situation, check if the array is NULL before performing qsort on it.

Signed-off-by: Mohan Yelugoti <ymdatta.work@gmail.com>

vector/v.external.out/list.c

@@ -53,7 +53,8 @@ char **format_list(int *count, size_t *len)
     }
 
     /* order formats by name */
-    qsort(list, *count, sizeof(char *), cmp);
+    if (list)
+        qsort(list, *count, sizeof(char *), cmp);
 #endif
 #if defined HAVE_POSTGRES && !defined HAVE_OGR
     list = G_realloc(list, ((*count) + 1) * sizeof(char *));