[BUG] Improved Barkskin cannot be used in Bear Form or Cat Form

[raethkcj]

1. Current Behavior

1.1. Description

Attempting to use Barkskin in a Feral form while the Improved Barkskin rune is engraved results in a "Must be in Tree Form" error message.

1.2. How to Reproduce

       1. Engrave the Improved Barkskin Rune on a helm
       2. Enter Dire Bear Form
       3. Cast Barkskin
       4. Observe error message and failure to cast

1.3 Source Material

2. Expected Behavior

2.1. Description

Improved Barkskin should be castable in any form, as described in the tooltip.

2.2 Source Material