From 9803f7f9f3fd50bc371ad04fe68fa66f7e20ac9d Mon Sep 17 00:00:00 2001
From: Zach Klippenstein <zach.klippenstein@gmail.com>
Date: Wed, 30 Dec 2015 01:56:50 -0800
Subject: [PATCH] Fixed a potential NPE when printing error cause chains.

---
 util/error.go      | 7 ++++++-
 util/error_test.go | 2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/util/error.go b/util/error.go
index 9246fe6..684ad50 100644
--- a/util/error.go
+++ b/util/error.go
@@ -176,7 +176,12 @@ func ErrorWithCauseChain(err error) string {
 			break
 		}
 	}
-	buffer.WriteString(err.Error())
+
+	if err != nil {
+		buffer.WriteString(err.Error())
+	} else {
+		buffer.WriteString("<err=nil>")
+	}
 
 	return buffer.String()
 }
diff --git a/util/error_test.go b/util/error_test.go
index bc902d6..375515a 100644
--- a/util/error_test.go
+++ b/util/error_test.go
@@ -23,6 +23,8 @@ caused by AssertionError: err2
 caused by err3`
 
 	assert.Equal(t, expected, ErrorWithCauseChain(err))
+
+	assert.Equal(t, "<err=nil>", ErrorWithCauseChain(nil))
 }
 
 func TestCombineErrors(t *testing.T) {