Version Information

Forge version: 14.23.5.2847
Botania version: r1.10-361

Further Information

Link to crash log:
crash-2019-10-10_18.49.57-client.txt

Steps to reproduce:

1. Share a page from the Lexica Botania
2. Try to open the link you shared while holding the book in your offhand (and in the inciting case, my main hand was empty, hence why it's trying to cast air)
3. ???
4. Profit... I mean crash!

What I expected to happen:
I was hoping it would either open the page I linked, or do nothing at all (either because I was sharing the page with myself or because, as seems to be the case, it can't find my book without crashing)
What happened instead:
Well... it crashed my client and confused the server proxy (The exception is also thrown there whenever I join, although it only crushed me when it initially happened and just kicks me now), for one thing, and now I can't get into my server without either deleting the affected player's data (mine) or rolling back the save (thankfully no one else was online at the time). More specifically, it looks like you may have forgotten to type-check before casting, and now you're trying to turn air into books (insert quip here about magically transmuting air and how this isn't Thaumcraft)? I'm just hypothesizing and I'm not very experienced with Java, so I could be off on that, but whatever you're doing, Minecraft doesn't like it.