Put the summary of the bug you're having here
I was on my server building a mob arena
What I expected to happen was...:
I was attempting to put down mob spawners and the first lines of code worked. But I was trying a new one.

What actually happened was...:
I used the following code:

/setblock ~ ~1 ~ minecraft:mob_spawner 0 replace {EntityId:Zombie,SpawnData:{Equipment:[{­id:276,Count:1}]},SpawnPotentials:[{Type­:Skeleton,Weight:1,Properties:{Equipment­:[{},{},{},{},{id:52}]}}],SpawnCount:2,S­pawnRange:3,RequiredPlayerRange:64,Delay­:10,MinSpawnDelay:10,MaxSpawnDelay:100,M­axNearbyEntities:2}

and it crashed my minecraft. Now I am unable to load that world.
Steps to Reproduce:
1. Put down a command block
2. Type or copy and paste the code from above into the command block
3. And then activate the block