tpl/time: Handle nil values in time.AsTime

Closes #8865

tpl/time/time.go

@@ -19,6 +19,8 @@ import (
 	"time"
 	_time "time"
 
+	"github.com/gohugoio/hugo/common/hreflect"
+
 	"github.com/gohugoio/hugo/common/htime"
 
 	"github.com/gohugoio/locales"
@@ -43,6 +45,9 @@ type Namespace struct {
 // AsTime converts the textual representation of the datetime string into
 // a time.Time interface.
 func (ns *Namespace) AsTime(v interface{}, args ...interface{}) (interface{}, error) {
+	if !hreflect.IsTruthful(v) {
+		return time.Time{}, nil
+	}
 	loc := ns.location
 	if len(args) > 0 {
 		locStr, err := cast.ToStringE(args[0])