fix missing roots message for nil classes

app/controllers/application_controller.rb

@@ -413,19 +413,20 @@ def get_class(params)
         # get the top level nodes for the root
         # TODO_REV: Support views? Replace old view call: @ontology.top_level_classes(view)
         @roots = @ontology.explore.roots(concept_schemes: params[:concept_schemes])
-        if @roots.nil? || @roots.empty?
+
+        if @roots.nil? || response_error?(@roots) || @roots.compact&.empty?
           LOG.add :debug, t('application.missing_roots_for_ontology', acronym: @ontology.acronym)
           classes = @ontology.explore.classes.collection
-          @concept = classes.first.explore.self(full: true) if classes.first
+          @concept = classes.first.explore.self(full: true) if classes&.first
           return
         end
 
         @root = LinkedData::Client::Models::Class.new(read_only: true)
-        @root.children = @roots.sort{|x,y| (x.prefLabel || "").downcase <=> (y.prefLabel || "").downcase}
+        @root.children = @roots.sort{|x,y| (x&.prefLabel || "").downcase <=> (y&.prefLabel || "").downcase}
 
         # get the initial concept to display
         root_child = @root.children&.first
-        not_found(t('application.missing_roots', id: @roots.id)) if root_child.nil?
+        not_found(t('application.missing_roots')) if root_child.nil?
 
         @concept = root_child.explore.self(full: true, lang: lang)
         # Some ontologies have "too many children" at their root. These will not process and are handled here.
@@ -445,7 +446,7 @@ def get_class(params)
         rootNode = @concept.explore.tree(include: include, concept_schemes: params[:concept_schemes], lang: lang)
         if rootNode.nil? || rootNode.empty?
           @roots = @ontology.explore.roots(concept_schemes: params[:concept_schemes])
-          if @roots.nil? || @roots.empty?
+          if @roots.nil? || response_error?(@roots) || @roots.compact&.empty?
             LOG.add :debug, t('application.missing_roots_for_ontology', acronym: @ontology.acronym)
             @concept = @ontology.explore.classes.collection.first.explore.self(full: true)
             return

config/locales/en.yml

@@ -66,7 +66,7 @@ en:
     provide_ontology_or_concept: Please provide an ontology id or concept id with an ontology id.
     search_for_class: Please search for a class using the Jump To field above
     missing_roots_for_ontology: Missing @roots for %{acronym}
-    missing_roots: Missing roots %{id}
+    missing_roots: Missing roots
     missing_class: Missing class %{root_child}
     missing_class_ontology: Missing class %{acronym} / %{concept_id}
     error_simplify_class: "Failure to simplify class: %{cls}"

config/locales/fr.yml

@@ -71,7 +71,7 @@ fr:
     provide_ontology_or_concept: Veuillez fournir un identifiant d'ontologie ou un identifiant de concept avec un identifiant d'ontologie.
     search_for_class: Veuillez rechercher une classe à l'aide du champ Jump To ci-dessus
     missing_roots_for_ontology: Racines manquantes pour %{acronym}
-    missing_roots: Racines manquantes %{id}
+    missing_roots: Racines manquantes
     missing_class: Classe manquante %{root_child}
     missing_class_ontology: Classe manquante %{acronym} / %{concept_id}
     error_simplify_class: "Échec de la simplification de la classe : %{cls}"