Creepers don't blow up grass blocks.

Put the summary of the bug you're having

What I expected to happen was...:
For the creeper to blow up and make a hole

What actually happened was...:
The creeper blew up but didn't blow up any grass blocks thus not making a hole at all. The grass blocks act like obsidian.

Steps to Reproduce:
1. Find a creeper
2. Walk up to it
3. Make it explode and nothing happens