From 56ccba86c7622333311e5fcb243815c9f3ddcaa3 Mon Sep 17 00:00:00 2001
From: Adrien Delorme <adrien.delorme@icloud.com>
Date: Mon, 15 Oct 2018 13:53:59 +0200
Subject: [PATCH] fix some race conditions

---
 packer/progressbar.go | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/packer/progressbar.go b/packer/progressbar.go
index f08928767..fed58f41a 100644
--- a/packer/progressbar.go
+++ b/packer/progressbar.go
@@ -66,7 +66,9 @@ func (spb *StackableProgressBar) Start(total int64) {
 func (spb *StackableProgressBar) Add(total int64) {
 	spb.mtx.Lock()
 	defer spb.mtx.Unlock()
-	spb.Bar.Add(total)
+	if spb.Bar.ProgressBar != nil {
+		spb.Bar.Add(total)
+	}
 }
 
 func (spb *StackableProgressBar) NewProxyReader(r io.Reader) io.Reader {
@@ -87,12 +89,13 @@ func (spb *StackableProgressBar) Finish() {
 	if spb.items == 0 {
 		// slef cleanup
 		spb.Bar.ProgressBar.Finish()
-		spb.Bar.ProgressBar = nil
 		spb.started = false
 		spb.total = 0
 		return
 	}
-	spb.prefix()
+	if spb.Bar.ProgressBar != nil {
+		spb.prefix()
+	}
 }
 
 // BasicProgressBar is packer's basic progress bar.