chore: branch is available when event is workflow_dispatch

[Tirke]

I'm not entirely sure why you don't always set the branch, especially since the branch can be overridden by the inputs to be always available, meaning the branch would always be set no matter the github event.

But I wanted to play it safe so I only added an exception for workflow_dispatch which always runs against a branch and we should always consider the branch in that case because otherwise we would pick from ci runs from all branches which is really bad.