Fix NPEs in protobuf conversion

[thelsing]

Identify the Bug or Feature request

related to #3254

Description of the Change

fixes NPEs. Tested Messages:
Heartbeat
SetCampain
PlayerConnected

Maybe we should rename the 1.13 branch to protobuf and squash-merge it into develop before 1.13. I guess there will be more fixes.

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This change is 

[cwisniew]

@thelsing there are a few

if (blah) do_something();

Can you please update to meet the coding standard

if (blah) {
   do_something();
}

I wish spotless google java plugin would enforce that rule but even though that is one of the rules for that format it doesnt enforce/reformat it.

Just makes things easier to read if everyone is doing the same thing.

We can merge this branch with develop after 1.12 which will probably be early to mid Jan (as protobuf stuff probably wont be tested enough for that release)

[thelsing]

I think it't best it this PR stays open until I test all messages. But on the other side: I can alway create a new PR.

[Phergus]

Just FYI, I'm going to leave this PR open as you requested until you tell me otherwise.

[thelsing]

I tested everything I can. So I think this should be merged into the release-1.13 branch. I have no idea how to test the ExecLink or ExecFunction and the non tested add-on messages in #3254
I would appreciate any help there.

[Phergus]

Reviewed 5 of 9 files at r1, 8 of 12 files at r2, 3 of 7 files at r3, 13 of 13 files at r4, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @thelsing)

[Phergus]

I have no idea how to test the ExecLink or ExecFunction and the non tested add-on messages in #3254

Not really functionality I've ever used but I'll see if I can throw something together for some basic testing.