`workbench.action.next|previousEditor` does not work across empty groups

[ngmariusz]

workbench.action.nextEditor and workbench.action.previousEditor works only if next/previous editors group is not empty what is possible (and requested) when workbench.editor.closeEmptyGroups is set to false

[bpasero]

Good catch, I argue this is even a bug and I think I have a fix for it.