Use begin/end instead of defined?

app/models/ci/commit.rb

@@ -205,11 +205,11 @@ module Ci
     end
 
     def ci_yaml_file
-      return @ci_yaml_file if defined?(@ci_yaml_file)
-
+      @ci_yaml_file ||= begin
         blob = project.repository.blob_at(sha, '.gitlab-ci.yml')
         blob.load_all_data!(project.repository)
-      @ci_yaml_file = blob.data
+        blob.data
+      end
     rescue
       nil
     end