fix(gui): Always show the "success" screen

Change-type: patch
Signed-off-by: Alexis Svinartchouk <alexis@resin.io>

lib/gui/modules/child-writer.js

@@ -85,22 +85,6 @@ const handleError = (error) => {
   terminate(EXIT_CODES.GENERAL_ERROR)
 }
 
-/**
- * @summary returns the last value in a Map
- * @param {Map} map - map
- * @returns {Any} the last value of the map (in insertion order)
- *
- * @example
- * const last = lastMapValue(map)
- */
-const lastMapValue = (map) => {
-  let value = null
-  for (value of map.values()) {
-    // eslint-disable-next-line no-empty
-  }
-  return value
-}
-
 /**
  * @summary writes the source to the destinations and valiates the writes
  * @param {SourceDestination} source - source
@@ -127,10 +111,6 @@ const writeAndValidate = (source, destinations, verify, onProgress, onFail, onFi
       )
     })
     .then(({ failures, bytesWritten }) => {
-    // If all destinations errored, treat the last fail as an error
-      if (failures.size === destinations.length) {
-        throw lastMapValue(failures)
-      }
       const result = {
         bytesWritten,
         devices: {