Send an empty keys array when there is no data

services/web/app/coffee/Features/References/ReferencesController.coffee

@@ -32,8 +32,8 @@ module.exports = ReferencesController =
 
 	_handleIndexResponse: (req, res, projectId, shouldBroadcast, data) ->
 		if !data? or !data.keys?
-			return res.send()
-		else if shouldBroadcast
+			return res.json({projectId, keys: []})
+		if shouldBroadcast
 			logger.log {projectId}, "emitting new references keys to connected clients"
 			EditorRealTimeController.emitToRoom projectId, 'references:keys:updated', data.keys
 		return res.json data

services/web/test/UnitTests/coffee/References/ReferencesControllerTests.coffee

@@ -134,9 +134,10 @@ describe "ReferencesController", ->
 					@res.sendStatus.calledWith(400).should.equal false
 					done()
 
-			it 'should close the response', (done) ->
+			it 'should send a response with an empty keys list', (done) ->
 				@call () =>
-					@res.send.called.should.equal true
+					@res.json.called.should.equal true
+					@res.json.calledWith({projectId: @projectId, keys: []}).should.equal true
 					done()
 
 	describe 'index', ->