Fixes #1409. Fixed: broken tab view decoded from xib in certain situation.

Without this fix, a tab view set up in Xcode where a tab but the first was selected could be instantiated in a corrupted state in Cappuccino, where tab selection would have no effect.

This fix ensures that even if the decoded view of the selected tab view item has a superview different from how we do things in Cappuccino, we make sure to set it right.