incorrectly formatted line in index file (line 1)

[companje]

this wifibox has the newest firmware but shows this error in the console:
UpdatePanel:checkStatus response: Object {data: Object, msg: "incorrectly formatted line in index file (line 1)", status: "fail"} doodle3d-client.min.js:1 UpdatePanel:setState: undefined > 1 ( ) (in Access Point Mode: undefined ) (newestVersion: undefined ) (refresh: false ) doodle3d-client.min.js:1 Printer:preheat: failed doodle3d-client.min.js:1

[peteruithoven]

Looks like it requests the images index file, but it receives our redirect / 404 page. (Which includes the "success" text we need to prevent captive portal popups on iOS devices)
This only happens when the WiFi-Box is in access point mode.

We should add a check and return a more appropriate error.
Maybe this check can be added to d3d-updater's downloadFile function.

[peteruithoven]

Moved: Doodle3D/doodle3d-firmware#48