Summary: Within `UIView+CSSLayout`, we often nil out the measure function of a node because view hierarchy can often change. Unfortunately, this causes us to hit an assert which crashes the app. Instead, lets the measure func to be set to NULL, regardless of how many children a node might have.
Reviewed By: emilsjolander
Differential Revision: D4148727
fbshipit-source-id: 79a0f3ef1bf7b1dce9a14de96f870e35c042b78b
e54af5e854