Shout out to all the Python programmers from the other frontpage thread who are responsible for bugs like this with their crappy scripting languages.
As surprising as it may be, bad code is often written by bad programmers. It doesn't matter what language you use if you write bad code.
Alternatively, some amazing tooling has been written in these "terrible" scripting languages. Instagram was sold for a billion dollars and was a glorified Python Django webapp ontop of a Postgres database.
I got in a similar debate with a coworker recently over some go code he wrote. He told me that go code didn't need full unit tests because the compiler checked for bugs. Amusingly, he swapped the order of two int arguments in a pull request literally an hour after our discussion. I pointed out how a unit test would have prevented the production regression he caused, and then he started writing tests for his changes. So yet again, scripting languages have nothing to do with "good" or "bad" code. It is all about good vs bad developers.
What happened in this case was that people used the literal value "NULL" to mean "I don't know". They could have used the word "LOLCAT" and the effect would have been the same. Overuse of in-band signalling is a general design flaw not specific to any programming language. (Remember when people would whistle a 2600Hz tone to make free phone calls? Same thing as this.)
null
NULL is not defined