Print error if index value in a page is wrong type

This was causing a panic with no information displayed about the
page causing the error.

diff --git a/hugolib/site.go b/hugolib/site.go
index 517c82dc3a1708ba9c12068abfe4ea70f3211f12..d6cd343cd2ecdde14eb18470ec94690a56208ace 100644 (file)
--- a/hugolib/site.go
+++ b/hugolib/site.go
@@ -362,8 +362,13 @@ func (s *Site) BuildSiteMeta() (err error) {
                        vals := p.GetParam(plural)
 
                        if vals != nil {
-                               for _, idx := range vals.([]string) {
-                                       s.Indexes[plural].Add(idx, s.Pages[i])
+                               v, ok := vals.([]string)
+                               if ok {
+                                       for _, idx := range v {
+                                               s.Indexes[plural].Add(idx, s.Pages[i])
+                                       }
+                               } else {
+                                       PrintErr("Invalid " + plural + " in " + p.File.FileName)
                                }
                        }
                }