[MC-66674] Summoning a FallingSand entity with {Block:"leaves"} crashes the client

Go in a world, any world, and type the following command:

/summon FallingSand ~ ~ ~ {Block:"leaves"}

It will crash your game. I provided the entire crash report as an attachment, also.

Environment

OS X Version 10.9.4
Processor: 1.8 GHz Intel Core i5
4GB 1600 MHz DDR3
Intel HD Graphics 4000
Java Version 7 Update 67

Confirmed for 14w32d

Comfired in 14w32d with folowing comand:
/summon FallingSand ~ ~10 ~ {Time:1,Block:minecraft:leaves,Data:0}