Remove useless checks for NULL before freeing

Remove useless checks for NULL before freeing

This patch has been generated by the following Coccinelle semantic patch:

// Remove useless checks for NULL before freeing
//
// free (NULL) is a no-op, so there is no need to avoid it

@@
expression E;
@@
+ free (E);
+ E = NULL;
- if (unlikely (E != NULL)) {
-   free(E);
(
-   E = NULL;
|
-   E = 0;
)
   ...
- }

@@
expression E;
@@
+ free (E);
- if (unlikely (E != NULL)) {
-   free (E);
- }