Don't use the trackChanges engine in the history editor panel

services/web/app/views/project/editor/editor.jade

@@ -39,7 +39,8 @@ div.full-size(
 			syntax-validation="settings.syntaxValidation",
 			review-panel="reviewPanel",
 			on-scroll="onScroll",
-			scroll-events="scrollEvents"
+			scroll-events="scrollEvents",
+			track-changes-enabled="true"
 		)
 		#review-panel
 			.review-panel-scroller

services/web/public/coffee/ide/editor/directives/aceEditor.coffee

@@ -48,6 +48,7 @@ define [
 				reviewPanel: "="
 				onScroll: "="
 				scrollEvents: "="
+				trackChangesEnabled: "="
 			}
 			link: (scope, element, attrs) ->
 				# Don't freak out if we're already in an apply callback
@@ -74,7 +75,7 @@ define [
 				highlightsManager     = new HighlightsManager(scope, editor, element)
 				cursorPositionManager = new CursorPositionManager(scope, editor, element, localStorage)
 				trackChangesManager   = new TrackChangesManager(scope, editor, element)
-				if window.location.search.match /tcon=true/ # track changes on
+				if scope.trackChangesEnabled and window.location.search.match /tcon=true/ # track changes on
 					trackChangesManager.enabled = true
 
 				# Prevert Ctrl|Cmd-S from triggering save dialog

services/web/public/coffee/ide/editor/directives/aceEditor/track-changes/TrackChangesManager.coffee

@@ -103,7 +103,7 @@ define [
 		recalculateReviewEntriesScreenPositions: () ->
 			session = @editor.getSession()
 			renderer = @editor.renderer
-			for entry_id, entry of @$scope.reviewPanel.entries
+			for entry_id, entry of (@$scope.reviewPanel?.entries or {})
 				doc_position = @_shareJsOffsetToAcePosition(entry.offset)
 				screen_position = session.documentToScreenPosition(doc_position.row, doc_position.column)
 				y = screen_position.row * renderer.lineHeight