When attempting to rename an item that already has a name longer than the anvil's text input box, the client crashes with the following:

java.lang.StringIndexOutOfBoundsException: String index out of range: 31 at java.lang.String.substring(String.java:1950) at net.minecraft.client.gui.GuiTextField.func_146175_b(SourceFile:162) at net.minecraft.client.gui.GuiTextField.func_146201_a(SourceFile:309) at de.mineformers.vanillaimmersion.client.gui.AnvilTextGui.func_73869_a(AnvilTextGui.kt:52) at net.minecraft.client.gui.GuiScreen.func_146282_l(GuiScreen.java:558) at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:512) at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1757) at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1096) at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:397) at net.minecraft.client.main.Main.main(SourceFile:123) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:483) at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

Full crash log here.