Fix infinite loop (bug #50083)

src/cache.c

@@ -2385,6 +2385,7 @@ is_busy(const dav_node *node)
     while (child) {
         if (is_busy(child))
             return 1;
+        child = child->next;
     }
 
     return (is_reg(node) && is_open_write(node));