When I attempt to run the mod from my client, the following error occurs:
Interestingly enough, I have no errors when attempting to run it via the runClient script.
This is the only line in which I call the registerCommand method:
ClientCommandHandler.instance.registerCommand(new TestSidebarScoresCommand());
I don't understand why this would happen, as the imported net.minecraftforge.client.ClientCommandHandler extends net.minecraft.command.CommandHandler, which contains this method.
Below is the command class, which extends CommandBase, which implements ICommand, meaning that it is the correct type for the parameter.
Sorry if this is a dumb mistake, I'm new to Forge and Gradle.
One last thing, the version of forge I'm using to write this in and the version that the client is in are the exact same, so it's not a version mismatch.