Silphaer

Can confirm: This happens on Linux and makes parkour obnoxiously difficult.

I can confirm this is real. I'll also give a little extra context detail, which this is lacking in.
When attempting to create a new superflat world, the game crashes as soon as I click on the "customise" button. On a customised world, it's fine, and lets me do it, but on superflat, it shows a brief glimpse of the dirt background screen, then crashes.
For me, I'm using Java 8 (I think) and Slackware 14.2. I found this the hard way. It's a very sad moment for anyone who uses superflat worlds.
EDIT:
I forgot to say before, I can also confirm that the same thing happens as soon as I enter "blocks".

Thanks, it's working now.

Thanks, and sorry, on my operating system it can be read by several different programs, I didn't think it would only allow access for GIMP.

This still does not work, unfortunately. I'm trying to create a map that re-creates the Siege of Helms Deep from Lord of the Rings, and my Orc spawners aren't detecting the player when they are inside the range, even though I have both the "RequiredPlayerRange" and "MaxNearbyEntities" in the same command.

This is my code: /setblock ~0 ~1 ~0 mob_spawner 0 replace {SpawnData:{HandItems:[{Count:1,id:iron_axe,tag:{Unbreakable:1,display:{Name:Orc Axe,Lore:[Orc Set Piece 1]},ench:[{id:16,lvl:1}]}},{}],ArmorItems:[{Count:1,id:iron_boots,tag:{Unbreakable:1,display:{Name:Orc Boots,Lore:[Orc Set Piece 5]},ench:[{id:3,lvl:1},{id:0,lvl:2}]}},{Count:1,id:iron_leggings,tag:{Unbreakable:1,display:{Name:Orc Leggings,Lore:[Orc Set Piece 4]},ench:[{id:3,lvl:1},{id:0,lvl:2}]}},{Count:1,id:iron_chestplate,tag:{Unbreakable:1,display:{Name:Orc Chestpiece,Lore:[Orc Set Piece 3]},ench:[{id:3,lvl:1},{id:0,lvl:2}]}},{Count:1,id:iron_helmet,tag:{Unbreakable:1,display:{Name:Orc Helmet,Lore:[Orc Set Piece 2]},ench:[{id:3,lvl:1},{id:0,lvl:2}]}}],CustomName:Orc,CustomNameVisible:1,Attributes:[{Name:generic.attackDamage,Base:3},{Name:generic.followRange,Base:80},{Name:zombie.spawnReinforcements,Base:0.1F}],HandDropChances:[0.2F,0.0F],ArmorDropChances:[0.1F,0.1F,0.1F,0.1F],Silent:1,PersistenceRequired:1,Health:25.0f,id:Zombie},SpawnCount:1,SpawnRange:2,maxNearbyEntities:10,requiredPlayerRange:200,Delay:10,MinSpawnDelay:40,MaxSpawnDelay:80}