make vote import more robust

app/controllers/votes_controller.rb

@@ -42,7 +42,15 @@ class VotesController < ApplicationController
         :voter_password => csv_fields[:voter_password],
       }
     }
-    Vote.upsert_all(votes, unique_by: [:user_id, :election_slug])
+    begin
+      Vote.upsert_all(votes, unique_by: [:user_id, :election_slug])
+    rescue
+      votes.each do |vote|
+        begin
+          Vote.upsert(vote, unique_by: [:user_id, :election_slug])
+        end
+      end
+    end
 
     respond_to do |format|
       format.html { redirect_to room_users_url(room_id), notice: 'Votes were successfully created.' }