Founders Cape doesn't appear on custom skins

The cape doesn't appear on custom skins.

 

Steps to reproduce this behavior:

1. Open the skin editor.

2. Select a regular skin.

3. Apply the Founders's cape.

4. Select a custom skin.

5. Apply the Founder's cape.

 

What happened:

The cape was applied and seen on regular skins.

The cape was applied but NOT seen on custom skins.

 

What was expected to happen:

The cape was applied and seen on regular skins.

The cape was applied and seen on custom skins as well.