[FEATURE REQUEST] Improve systray context menu

[ppvnf]

• I believe No updates are available would be better if self.availableUpdates == 0:

• Grey out/disable No updates are available (I've no idea how to do that):

Related to #446 and #447

[ppvnf]

Maybe I should've used the bug label

[marticliment]

Done!

[ppvnf]

Thanks! It will be possible to translate the keys "1 update was found" and "No updates are available" after a new version is released, right?

[marticliment]

it will be possible when I add the key in tolgee, which I'll probably do soon