Attention some PRs have been merged in another branch

[Neustradamus]

@vukoye: Attention some PRs have been merged in another branch:

• https://github.com/vukoye/xmpp_dart/tree/null_safety

[TatankaConCube]

now we have development branch before releasing next stable version

[Neustradamus]

@vukoye, @TatankaConCube: The selected branch is alwyas in master.

Can you look?

Thanks in advance.