I'm so glad I'm not your junior then. I prefer to work at companies who actually ship products instead of going around fixing 3rd party bugs.
So you're okay with 3rd-party features, which you willingly import into your project and utilize to make your job easier, but you're not okay with taking responsibility for any bugs in those 3rd-party libraries. Doesn't make any sense. I'm glad you're not my junior, too.
Were you my junior, telling this to me as your project manager, I'd demand you fix the bug. The reason is - we already gained from your decision to advance the project by including the external work, and at the moment you included it in your project you accepted responsibility for the issue. Failing to take responsibility for this code, whether you wrote it or not, would be a major distraction from the task, and thus does not reflect positively on you as a developer...