Brief explanation of issue: When adding a new line to the clipboard, I can cause the entire game to crash.

Steps to reproduce:

• Step 1 Open a clipboard and add text to any line, anywhere.
• Step 2 Before clicking anything else, press the arrow to go to the next page.
  BOOM instant crash, repeatable every time.

Not that anyone would need to do it, but I did it by accident and was able to reproduce it so heres a report.

Link to crash report (if applicable) on gist:

ShadowMC version: 1.12-3.8.0

Minecraft version: 1.12.2