Return an empty list and never null from list-valued parameters in generated models

We have something like this:
// check if empty
if (myObjects.getListParam() == null || myObjects.getListParam().size() == 0) {
    // ...
}

becomes:
if (myObjects.getListParam().size() == 0) {
    // ...
}

And this:

if (myObjects.getListParam() != null) {
    for (ListValue v : myObjects.getListParam()) {
        // ...
    }
}

becomes:
for (ListValue v : myObjects.getListParam()) {
    // ...
}