Summary:
We need to check the existence of RCTLinkingManager (which doesn't exist on Android) because this code is called on require.
Closes https://github.com/facebook/react-native/pull/5680
Reviewed By: svcscm
Differential Revision: D2887260
Pulled By: androidtrunkagent
fb-gh-sync-id: 4a5843ea6a5898d0f2810ad9ddb5b2078054e9f1