Summary:
Strangely comparing a pointer with zero will only be a clang warning when compiling with `-Wpedantic`, so this incorrect comparison is silently allowed.
**Test plan**
Compiles with `-Wpedantic`.
Closes https://github.com/facebook/react-native/pull/11709
Differential Revision: D4377512
Pulled By: ericvicenti
fbshipit-source-id: 483cf1f41d3f539c452d542ad2155c4c4b41616d