Can constructor return a null object?

No, it has never been possible. Maybe a previous version of the code used some factory method which could return null:

MyObject o = createMyObject("parameter");
if (o == null) o = createMyObject("fallback parameter");

From section 15.9.4 of the JLS:

The value of a class instance creation expression is a reference to the newly created object of the specified class. Every time the expression is evaluated, a fresh object is created.

So no, it can never return null.

My guess is that it was written by a C programmer who is used to testing the return value of malloc() for NULL, malloc() can return NULL if your system runs out of memory.

The code doesn't make sense in Java since Java will throw an OutOfMemoryError` if it runs out of memory.

The code is dead in any version of Java. It's not possible for a constructor to return null, and even if an exception would be thrown from the constructor, the next line won't be called.