Summary:
At some early stages of Instance initialization, it does not have a `nativeToJsBridge_`. At the same time, `handleMemoryPressure` can be called at any point in time, so we should check the pointer for not being null before calling on it.
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: JoshuaGross, mdvacca
Differential Revision: D21798522
fbshipit-source-id: 6384da88784cceb493cf9810408cbb47777d3f4b