Forge Version 1.12.2-14.23.5.2838 broken

[ShadeZinc46]

Ok, first of all, the reason I'm using this version and not the latest is because is the version RLCraft servers run on, and I'm trying to start one. So I download the win-installer from the website, open it aaaaaand nothing happens. I reinstall java, nothing. I run it with command prompt using this command (yes, I renamed the file to forge.jar for easier typing):

java -Xmx2G -jar forge.jar

and it gives me this error:

java.net.preferIPv4Stack=true
Exception in thread "main" java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at net.minecraftforge.installer.Java6Gate.main(Java6Gate.java:48)
Caused by: java.lang.ExceptionInInitializerError
	at net.minecraftforge.installer.ClientInstall.getSponsorMessage(ClientInstall.java:401)
	at net.minecraftforge.installer.InstallerAction.getSponsorMessage(InstallerAction.java:60)
	at net.minecraftforge.installer.InstallerPanel.updateFilePath(InstallerPanel.java:334)
	at net.minecraftforge.installer.InstallerPanel.<init>(InstallerPanel.java:315)
	at net.minecraftforge.installer.SimpleInstaller.launchGui(SimpleInstaller.java:167)
	at net.minecraftforge.installer.SimpleInstaller.main(SimpleInstaller.java:54)
	... 5 more
Caused by: java.lang.ArrayIndexOutOfBoundsException: 1
	at net.minecraftforge.installer.MirrorData.buildMirrorList(MirrorData.java:84)
	at net.minecraftforge.installer.MirrorData.<init>(MirrorData.java:63)
	at net.minecraftforge.installer.MirrorData.<clinit>(MirrorData.java:17)
	... 11 more

Can anyone help me?

[Luis_ST]

1.12 is no longer supported on this forum.
Please update to a modern version of Minecraft to receive support.