text/template: make zero Template work again

Fixes #11379.

Change-Id: Idbb5c3faad472b77e9867dd2d4551fef5e4ac5f1
Reviewed-on: https://go-review.googlesource.com/11421
Reviewed-by: Rob Pike <r@golang.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/src/text/template/exec.go b/src/text/template/exec.go
index 8e9edcfbe9..daba788b55 100644
--- a/src/text/template/exec.go
+++ b/src/text/template/exec.go
@@ -113,7 +113,10 @@ func errRecover(errp *error) {
 // the output writer.
 // A template may be executed safely in parallel.
 func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error {
-	tmpl := t.tmpl[name]
+	var tmpl *Template
+	if t.common != nil {
+		tmpl = t.tmpl[name]
+	}
 	if tmpl == nil {
 		return fmt.Errorf("template: no template %q associated with template %q", name, t.name)
 	}
@@ -146,6 +149,9 @@ func (t *Template) Execute(wr io.Writer, data interface{}) (err error) {
 // it returns the empty string. For generating an error message here
 // and in html/template.
 func (t *Template) DefinedTemplates() string {
+	if t.common == nil {
+		return ""
+	}
 	var b bytes.Buffer
 	for name, tmpl := range t.tmpl {
 		if tmpl.Tree == nil || tmpl.Root == nil {