More guarding against freeing NULL pointers.

src/list.c

@@ -25,6 +25,7 @@ void
 list_free(l)
   list *l;
 {
+  if (l) {
     list_item *li, *tmp;
 
     pthread_mutex_lock(&(l->mutex));
@@ -33,7 +34,6 @@ list_free(l)
       li = l->head;
       while (li != NULL) {
         tmp = li->next;
-      zfree(li);
         li = tmp;
       }
     }
@@ -41,6 +41,7 @@ list_free(l)
     pthread_mutex_unlock(&(l->mutex));
     pthread_mutex_destroy(&(l->mutex));
     zfree(l);
+  }
 }
 
 list_item *

src/token.c

@@ -21,11 +21,15 @@ str_array * str_array_create(int cap) {
 }
 
 void str_array_free(str_array *l) {
+    if (l) {
         for ( int i = 0; i < l->len ; i++ ) {
             char * t = l->tokens[ i ];
+            if (t) {
                 zfree(t);
             }
+        }
         zfree(l);
+    }
 }
 
 bool str_array_is_full(str_array * l) {