Google Drive _getFile doesn't check if a file ID exists before using it

[stuartlangridge]

In _getFile at https://github.com/remotestorage/remotestorage.js/blob/5b580e8e959a34e7ed2ab89e417929ebb3d04c90/src/googledrive.ts#L476 and https://github.com/remotestorage/remotestorage.js/blob/5b580e8e959a34e7ed2ab89e417929ebb3d04c90/src/googledrive.ts#L477 the Google Drive backend retrieves a file ID but doesn't check that that file ID exists before using it in a request, leading to (if the requested file doesn't exist at all in Google Drive and so has no ID) requests being made to https://www.googleapis.com/drive/v2/files/undefined which is definitely wrong.

This isn't a PR because I'm not sure what should happen here; should that function throw an error, or fake a response object with statusCode 404, or something else?

[raucao]

This isn't a PR because I'm not sure what should happen here; should that function throw an error, or fake a response object with statusCode 404, or something else?

Faking a 404 seems like a reasonable option to me. I guess any potential issues with that approach would become apparent once you implement and test it.