Withers don't attack when summoned via command

When you summon a wither in survival, the wither doesn't attack the player or anything nearby example: pigs, horses, etc. This is a bug when a wither is summoned via command line.

Steps to reproduce

• Be in Survival.
• Summon a wither. (Easy-Hard mode. Cheats Enabled.)
• Notice that the wither is just hovering.