Summary:
Motivation: When viewing a stack trace in YellowBox where one or more of the stack frames has no `file`, JS will encounter the fatal error `null is not an object (evaluating 'file.split')`. This can happen, for example, when running a bundle for which no source maps were generated.
Closes https://github.com/facebook/react-native/pull/13512
Differential Revision: D4896480
Pulled By: javache
fbshipit-source-id: 202c793a47abb83a4700a5778a92b0b5828b01a3