Catch error on export
Catch error on export

Summary:
`exportStore` throws, when no device is connected. The error wasn't catched and `process.exit();` never called. The result is that the CLI couldn't be interrupted as long as `exportStore` thorws (e.g. no device connected).

Catching this error now.

Reviewed By: passy

Differential Revision: D14520754

fbshipit-source-id: 97b245c4de53e58bac8066a1b15874d873bf2841

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