Fix broken URL export

Summary:
Fixes broken export through URL.
Also fixes an issue where we suppress an exception

Reviewed By: mweststrate

Differential Revision: D19517066

fbshipit-source-id: c68b6a1bcbc8b0588e0db9032268033a42b43c61

src/utils/exportData.tsx

@@ -607,7 +607,7 @@ export async function exportStore(
 
 export const exportStoreToFile = (
   exportFilePath: string,
-  store: Store,
+  store: MiddlewareAPI,
   idler?: Idler,
   statusUpdate?: (msg: string) => void,
 ): Promise<{errorArray: Array<Error>}> => {