[Possible bug] Feat: Two Weapon Defense stacking

[chaoxinhu]

Version 3.2.8, Feat: Two Weapon Defense has two issues:

1. It grants a Shield AC bonus. However, this bonus stacks with item "Shield Amulet" (purchased from Malavon). Given the fact that this bonus does NOT stack with spell "Shield", this might be a bug?
2. In some cases, this bonus still applies even after two weapons are unequipped. This can be reproduced if you are a Kensei/Monk/Ranger with two weapon defense feat.