From 661a1e90263cc348c17620cf0b250bf552dd4056 Mon Sep 17 00:00:00 2001
From: Victor Vieux <vieux@docker.com>
Date: Tue, 17 Jun 2014 20:45:57 +0000
Subject: [PATCH] prevent panic when empty flag

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
---
 pkg/mflag/flag.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pkg/mflag/flag.go b/pkg/mflag/flag.go
index 2cfef331f6..ad23e540fb 100644
--- a/pkg/mflag/flag.go
+++ b/pkg/mflag/flag.go
@@ -778,6 +778,9 @@ func (f *FlagSet) usage() {
 }
 
 func trimQuotes(str string) string {
+	if len(str) == 0 {
+		return str
+	}
 	type quote struct {
 		start, end byte
 	}