Make the tab item at tabItemPath the active one, deactivating the rest of
its block. This is the single writer of the one-active-item invariant: it
also repairs a block that has drifted to zero or several active items.
Returns null when the path is not a tab item or nothing would change.
Make the tab item at
tabItemPaththe active one, deactivating the rest of its block. This is the single writer of the one-active-item invariant: it also repairs a block that has drifted to zero or several active items. Returns null when the path is not a tab item or nothing would change.