/fill bug

Put the summary of the bug you're having here
I thought using /fill and filling with slimeblocks would be cool
Describe what you thought should happen here
I was using the /fill command and tried fill with slimeblocks, then the game crashed, and when I joined again minecraft crashed again
Describe what happened here
Steps to Reproduce:
1. /fill 261 3 -731 268 15 -714 minecraft:slime
2. ...
3. ...