tweaks for Playing Track in a tab

[mikebo]

Since the Playing Track tab doesn't allow changing nodes and will reopen when new track starts playing then maybe it should have the tab options: lock tab & disable left navigator ticked by default and grayed out.

[mikebo]

ok it turns out that the Playing Track tab was reopening because i was closing the inactive tab with a middle click (bug?).
But the left-navigator suggestion still stands. Instead of making me feel like a fool and showing me an error saying the left navigator is disabled when i try to change the node, just make it look disabled

[KangNi]

1+