fix(nylas-api): Fix broken promise logic in NylasAPI success/error blocks

- Restores file uploading / canceling behavior

src/flux/nylas-api.coffee

@@ -187,20 +187,20 @@ class NylasAPI
     success = (body) =>
       if options.beforeProcessing
         body = options.beforeProcessing(body)
-        return Promise.resolve(body)
       if options.returnsModel
         @_handleModelResponse(body).then (objects) ->
           return Promise.resolve(body)
+      Promise.resolve(body)
 
     error = (err) =>
+      handlePromise = Promise.resolve()
       if err.response
-        handlePromise = Promise.resolve()
         if err.response.statusCode is 404 and options.returnsModel
           handlePromise = @_handleModel404(options.url)
         if err.response.statusCode is 401
           handlePromise = @_handle401(options.url)
-        handlePromise.then ->
-          Promise.reject(err)
+      handlePromise.finally ->
+        Promise.reject(err)
 
     req = new NylasAPIRequest(@, options)
     req.run().then(success, error)

src/flux/tasks/change-category-task.coffee

@@ -44,10 +44,6 @@ class ChangeCategoryTask extends Task
         if @threadIds.length > 0 then Klass = Thread
         else if @messageIds.length > 0 then Klass = Message
         DatabaseStore.find(Klass, objectId).then (object) =>
-          # Always apply our changes to a new copy of the thread.
-          # In some scenarios it may actually be frozen
-          object = new Klass(object)
-
           # Mark that we are optimistically changing this model. This will prevent
           # inbound delta syncs from changing it back to it's old state. Only the
           # operation that changes `optimisticChangeCount` back to zero will

src/flux/tasks/change-labels-task.coffee

@@ -1,4 +1,5 @@
 _ = require 'underscore'
+Task = require './task'
 Label = require '../models/label'
 Thread = require '../models/thread'
 Message = require '../models/message'