Timeline: fix NPE when hovering over Interactions strip

third_party/WebKit/Source/devtools/front_end/timeline/TimelineFlameChart.js

Index: third_party/WebKit/Source/devtools/front_end/timeline/TimelineFlameChart.js
diff --git a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineFlameChart.js b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineFlameChart.js
index 42aad625090028d17eff7ee412c983b23c0d2c77..356dd8ecb37d8d62e3fa297e4c837e3de903d486 100644
--- a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineFlameChart.js
+++ b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineFlameChart.js
@@ -497,9 +497,9 @@ Timeline.TimelineFlameChartDataProvider = class {
    */
   highlightEntry(entryIndex) {
     SDK.DOMModel.hideDOMNodeHighlight();
-    var event = /** @type {!SDK.TracingModel.Event} */ (this._entryData[entryIndex]);
-    if (!event)
+    if (this._entryType(entryIndex) !== Timeline.TimelineFlameChartEntryType.Event)
       return;
+    var event = /** @type {!SDK.TracingModel.Event} */ (this._entryData[entryIndex]);
     var target = this._model.targetByEvent(event);
     if (!target)
       return;