Affects Version/s: 1.5.3, 126.96.36.199 Beta
Fix Version/s: None
Platform:Windows 10 - PC
Monster spawners are not showing mobs or entities after middle clicking the spawner with CRTL + Middle Click and placing on the ground the mob/entity will not render and spawner will appear empty like so in these screenshots.
1. You need to create a mob spawner with a mob by placing the spawner on the ground and placing a spawn egg in it.
2. You need next CTRL + MIDDLE CLICK the spawner to get a spawner of that mob.
3. Then finally you need to place the Mob spawner block.
As you can see the Spawner on the right-hand side does not display the mob of a ghast mob.
Thanks for taking a look into this and have a nice day.