Don't worry about not having made many or even any open source code contributions. You probably don't want to work for or with any person or any organization that will judge you negatively based on that.
True open source software development is about sharing code because you want to do so. It's not about crafting reams and reams of crappy JavaScript or Ruby code just to be able to claim to be a "prolific contributor", or to brag about having made a large number of GitHub pull requests.
Writing closed-source code that solves real problems is more valuable and important than writing open source software that only serves to stroke one's ego.
True open source software development is about sharing code because you want to do so. It's not about crafting reams and reams of crappy JavaScript or Ruby code just to be able to claim to be a "prolific contributor", or to brag about having made a large number of GitHub pull requests.
Writing closed-source code that solves real problems is more valuable and important than writing open source software that only serves to stroke one's ego.