Issue Description:

Glider is found in every category, even in the "Delete item" slot.
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Steps to reproduce (important):

1. Go into a creative mode game with the mod installed.
2. Open the creative inventory.
3. Chose a category.
4. Scroll until you find the hang glider items.
5. Repeat for all other categories.
   ...

Affected Versions (Do not use "latest". Forge version is nice, but not usually necessary.):

• OpenGlider: 1.0.0
• Minecraft: 1.12
• Forge: 1.12-14.21.1.2420

Update the mod and it will be fixed

Fixed in this commit