Expected behaviour: mobGriefing prevents entities from destroying blocks

What happens: fireballs exploding close enough to a dripleaf will destroy it

Steps to reproduce:

• Enter a creative world, with cheats enabled
• Place a small dripleaf plant on clay and bonemeal it until a large dripleaf appears
• Run these commands:
• /gamerule mobGriefing false
• /summon fireball ^ ^ ^1
• Punch the fireball near the dripleaf (the explosion has to occur within ~1 block of the top of the plant; you may need a backboard since the dripleaf is intangible)
• The explosion will destroy the dripleaf plant and its stem