From 25191a24433a4744b02a2e77dbed7a77fe2c840e Mon Sep 17 00:00:00 2001
From: mcrakhman <rakhmanov.m@gmail.com>
Date: Sat, 3 Dec 2022 15:59:45 +0100
Subject: [PATCH] Fix dfsprev

---
 common/pkg/acl/tree/tree.go | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/common/pkg/acl/tree/tree.go b/common/pkg/acl/tree/tree.go
index 80bbb78c..f1dbbf9b 100644
--- a/common/pkg/acl/tree/tree.go
+++ b/common/pkg/acl/tree/tree.go
@@ -336,8 +336,9 @@ func (t *Tree) dfsPrev(stack []*Change, breakpoints []string, visit func(ch *Cha
 		t.visitedBuf = append(t.visitedBuf, ch)
 
 		for _, prevId := range ch.PreviousIds {
-			prevCh := t.attached[prevId]
-			if !prevCh.visited {
+			prevCh, exists := t.attached[prevId]
+			// here the only time it wouldn't exist if we are at the tree root
+			if exists && !prevCh.visited {
 				stack = append(stack, prevCh)
 			}
 		}