net/url: simplify value lookup

Change-Id: Ic998c189003d4dee758fca3b5ac954d5b54d3d36
Reviewed-on: https://go-review.googlesource.com/19764Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/url/url.go

@@ -709,8 +709,8 @@ func (v Values) Get(key string) string {
 	if v == nil {
 		return ""
 	}
-	vs, ok := v[key]
-	if !ok || len(vs) == 0 {
+	vs := v[key]
+	if len(vs) == 0 {
 		return ""
 	}
 	return vs[0]