I don't write Java, but support an application written in Java that gets null pointer issues and aborts all the time. It's also annoying that there is precious little information for me to go on.
Its not a very clear error, but you can narrow down the issue to a few things even when doing application support.
I believe that if you support it long enough, it's your application now, so no one else is to blame. How long is long enough? I'd say 1k-2k of lines of code per month of supporting it should be pretty reasonable. So if you supported a project of 10k lines for a year -- it's yours now, stop blaming original authors.
Good engineer would start improving it little-by-little, or convince manager that they need to spend some time on refactoring some piece of it. That differentiates a coder from an engineer.