Don't allow to modify answer's documents for started polls

app/models/abilities/administrator.rb

@@ -124,7 +124,9 @@ module Abilities
       cannot :comment_as_moderator, [::Legislation::Question, Legislation::Annotation, ::Legislation::Proposal]
 
       can [:create], Document
-      can [:destroy], Document, documentable_type: "Poll::Question::Answer"
+      can [:destroy], Document do |document|
+        document.documentable_type == "Poll::Question::Answer" && can?(:update, document.documentable)
+      end
       can [:create, :destroy], DirectUpload
 
       can [:deliver], Newsletter, hidden_at: nil

app/models/abilities/common.rb

@@ -71,7 +71,7 @@ module Abilities
       can [:create, :destroy], Follow, user_id: user.id
 
       can [:destroy], Document do |document|
-        document.documentable&.author_id == user.id
+        document.documentable_type != "Poll::Question::Answer" && document.documentable&.author_id == user.id
       end
 
       can [:destroy], Image do |image|