Add menu tests for pages with both Yaml and Toml front matter

See #817

hugolib/site.go

@@ -644,6 +644,7 @@ func (s *Site) assembleMenus() {
 		for name, me := range p.Menus() {
 			if _, ok := flat[twoD{name, me.KeyName()}]; ok {
 				jww.ERROR.Printf("Two or more menu items have the same name/identifier in %q Menu. Identified as %q.\n Rename or set a unique identifier. \n", name, me.KeyName())
+				continue
 			}
 			flat[twoD{name, me.KeyName()}] = me
 		}