Move file locking feature check to FileLock helper

app/views/projects/blob/_header.html.haml

@@ -11,7 +11,6 @@
       = view_on_environment_button(@commit.sha, @path, @environment) if @environment
 
     .btn-group{ role: "group" }<
-      - if @project.feature_available?(:file_locks)
       = lock_file_link(html_options: { class: 'btn btn-sm path-lock' })
 
       = edit_blob_button

ee/app/helpers/ee/lock_helper.rb

 module EE
   module LockHelper
     def lock_file_link(project = @project, path = @path, html_options: {})
+      return unless project.feature_available?(:file_locks)
       return unless current_user
       return if path.blank?