Fix API implementation

lib/api/builds.rb

@@ -79,9 +79,7 @@ module API
           return redirect_to build.artifacts_file.url
         end
 
-        unless artifacts_file.exists?
-          not_found!
-        end
+        return not_found! unless artifacts_file.exists?
 
         present_file!(artifacts_file.path, artifacts_file.filename)
       end

lib/api/entities.rb

@@ -406,7 +406,7 @@ module API
           repo_obj.artifacts_download_url
         end
       end
-      expose :artifacts_file, using: BuildArtifactFile, if: lambda { |build, opts| build.artifacts? }
+      expose :artifacts_file, using: BuildArtifactFile, if: -> (build, opts) { build.artifacts? }
       expose :commit, with: RepoCommit do |repo_obj, _options|
         if repo_obj.respond_to?(:commit)
           repo_obj.commit.commit_data