java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

What the log looks like

java\.lang\.IndexOutOfBoundsException: Index: 0, Size: 0
IndexOutOfBoundsException: Index: 0, Size: 0\r?\n\s+at java\.util\.ArrayList\.rangeCheck

How to fix it

1. Open your crash report or latest.log and locate java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 (if it appears inside a 'Caused by:' section lower down, read that section first).
2. Skip past java.util.ArrayList.rangeCheck, java.util.ArrayList.get, and any net.minecraft lines to find the very first mod or plugin class directly beneath them (for example, su.plo.voice / [plasmo_voice:?] or org.spongepowered). Ignore API or event-bus mods listed further down such as architectury or net.minecraftforge.eventbus.
3. Update the identified mod, plugin, or server software (such as SpongeForge) to its newest build for your Minecraft version, since missing empty-list checks are code bugs fixed by developers in updates.
4. If the crash triggers immediately when opening a mod GUI or settings screen (such as Plasmo Voice settings), verify your required hardware/audio devices are active or delete that mod's file inside the config folder to regenerate fresh defaults.
5. If the issue persists on the latest version, disable that specific mod or send the full log to its issue tracker rather than reporting it to API libraries mentioned lower in the trace.

Check your own log