b_free() fix crash on NULL

buffer.c

@@ -548,6 +548,8 @@ Buffer* b_pack(Buffer* const pBD) {
  * Return value: N/A
  */
 void b_free(Buffer* const pBD) {
+    if (pBD){
         free(pBD->cb_head);
         free(pBD);
+    }
 }