WIP: fix crash when adding file attachment to problem

There was an incomplete rename in commit 1e93118 (enable file
attachments for problems, with shared code for filelinks of groups and
problems, 2013-12-19). Triggers error when trying to add a file
attachment to a problem and there is a validation failure.

app/controllers/filelinks/roots_controller.rb

@@ -80,11 +80,11 @@ def create
     self.model = load_model
     authorize model, :update?
     authorize FileAttachment.find(filelink_params[:file_attachment_id]), :use?
-    @new_file = model.filelinks.build(filelink_params)
-    if @new_file.save
+    @new_filelink = model.filelinks.build(filelink_params)
+    if @new_filelink.save
       redirect_to(index_path, :notice => "File attachment added")
     else
-      @files = model.filelinks.order(:filepath)
+      @filelinks = model.filelinks.order(:filepath)
       render :action => :index
     end
   end