FIX: Post with multiple polls containing votes can not be edited.

https://meta.discourse.org/t/500-internal-server-error-when-editing-specific-poll-in-a-post-with-votes-editing-other-polls-works-fine/59684

plugins/poll/lib/polls_updater.rb

@@ -79,6 +79,7 @@ module DiscoursePoll
             if previous_option["id"] != option["id"]
               if votes_fields = post.custom_fields[DiscoursePoll::VOTES_CUSTOM_FIELD]
                 votes_fields.each do |key, value|
+                  next unless value[poll_name]
                   index = value[poll_name].index(previous_option["id"])
                   votes_fields[key][poll_name][index] = option["id"] if index
                 end

plugins/poll/spec/lib/polls_updater_spec.rb

@@ -217,6 +217,40 @@ describe DiscoursePoll::PollsUpdater do
       end
     end
 
+    it 'should be able to edit multiple polls with votes' do
+      DiscoursePoll::Poll.vote(
+        post_with_two_polls.id,
+        "poll",
+        [two_polls["poll"]["options"].first["id"]],
+        user
+      )
+
+      raw = <<-RAW.strip_heredoc
+      [poll]
+      * 12
+      * 34
+      [/poll]
+
+      [poll name=test]
+      * 12
+      * 34
+      [/poll]
+      RAW
+
+      different_post = Fabricate(:post, raw: raw)
+      different_polls = DiscoursePoll::PollsValidator.new(different_post).validate_polls
+
+      message = MessageBus.track_publish do
+        described_class.update(post_with_two_polls.reload, different_polls)
+      end.first
+
+      expect(post_with_two_polls.reload.custom_fields[DiscoursePoll::POLLS_CUSTOM_FIELD])
+        .to eq(different_polls)
+
+      expect(message.data[:post_id]).to eq(post_with_two_polls.id)
+      expect(message.data[:polls]).to eq(different_polls)
+    end
+
     describe "when poll edit window has expired" do
       let(:poll_edit_window_mins) { 6 }
       let(:another_post) { Fabricate(:post, created_at: Time.zone.now - poll_edit_window_mins.minutes) }