Defining an entry with no pages crashes the game on 1.16

[blockgoblin31]

Mod loader

Forge

Minecraft version

1.16.5

Patchouli version

1.16.4-53.3

Modloader version

Forge 36.2.34

Modpack info

https://github.com/tuc56/processing-pack/tree/patchouli-book

The latest.log file

https://gnomebot.dev/paste/1028101056074367076

Issue description

When loading an entry with no pages(in this case to make sure my icon is correct), you can open the entry fine, but upon trying to exit(I used shift click instead of normal click), the game crashes.

Steps to reproduce

1. Define an entry with a valid name, icon, and category, but no pages
2. reload your book and open the entry
3. Shift click the back button to go back to the main page of the book

Other information

there are a few scripts that weren't on the github; I honestly don't remember what. the modlist.html includes everything, though.
The paste site is the one used when you upload a file in the modded minecraft discord. It's personally my favorite option for crash highlighting.

[williewillus]

Seems like not an issue on 1.19. Not sure I have time to get to it but if anyone wants to send a patch for it I'll apply it to 1.16 for the next bugfix release, whenever that will be.