template: fix trivial bug: integers are not "empty"

Fixes #1357.

R=adg, gri
CC=golang-dev
https://golang.org/cl/3809041

src/pkg/template/template.go

@@ -673,7 +673,7 @@ func empty(v reflect.Value) bool {
 	case *reflect.SliceValue:
 		return v.Len() == 0
 	}
-	return true
+	return false
 }
 
 // Look up a variable or method, up through the parent if necessary.

src/pkg/template/template_test.go

@@ -197,6 +197,12 @@ var tests = []*Test{
 		out: " Header\n",
 	},
 
+	&Test{
+		in: "{.section integer}{@}{.end}",
+
+		out: "77",
+	},
+
 	// Repeated
 	&Test{
 		in: "{.section pdata }\n" +