[#3590] Prevent suspicious NPE forn Gradle SubProjectsNode

[lkishalmi]

This one prepares the code getting null from ProjectUtils.getContainedProjects()

---

^Add meaningful description above

By opening a pull request you confirm that, unless explicitly stated otherwise, the changes -

• are all your own work, and you have the right to contribute them.
• are contributed solely under the terms and conditions of the Apache License 2.0 (see section 5 of the license for more information).

Please make sure (eg. git log) that all commits have a valid name and email address for you in the Author field.

If you're a first time contributor, see the Contributing guidelines for more information.

[neilcsmith-net]

Possibly looking at needing an rc4 for NB13 (also NPE related). Maybe this is one to get in too if we do?

[lkishalmi]

Well, if we need an RC4 this one could be there as it is trivial.
So if you ping me or the team that we are doing an rc4 I'm gladly rebase this one.

[lkishalmi]

@neilcsmith-net Just rebased on delivery. Take this if you wish. It seems I need to take a few strolls on the shores of the Pacific Ocean (wife orders), so I won't be around for a while.

[neilcsmith-net]

Thanks @lkishalmi - and enjoy your strolls!