But the point is you can’t provide an external tool to implement what would be a language’s core feature. Otherwise if you are using IntelliJ IDEA you’ll be fine, but your colleagues who use, say, Eclipse, or anything else, will not, and so you will keep tracking down their null references.
Having said that, null references at compile time are not particularly tricky. What is tricky is runtime null references. For that you need robust support from the language.