dave

Got the crash report

Found out how to fix in singleplayer, you need to change the version to 1.7.10 and then load the world. Some stuff might be gone, but the spawner doesnt work.
*Still don't know how to fix in multiplayer servers/ realms

If you wanna try it out here is the command:

/setblock ~ ~ ~ minecraft:mob_spawner 0 replace {EntityId: ArmorStand}