[PointerLock] Add null check before dispatching click event

third_party/WebKit/Source/core/page/PointerLockController.cpp

Index: third_party/WebKit/Source/core/page/PointerLockController.cpp
diff --git a/third_party/WebKit/Source/core/page/PointerLockController.cpp b/third_party/WebKit/Source/core/page/PointerLockController.cpp
index 6c00982d5fa06abe5040104b4f7495a1f8a4a626..f9aa43bb099a1c7c5ab1b8665362ec992695742c 100644
--- a/third_party/WebKit/Source/core/page/PointerLockController.cpp
+++ b/third_party/WebKit/Source/core/page/PointerLockController.cpp
@@ -140,6 +140,10 @@ void PointerLockController::DispatchLockedMouseEvent(
 
   element_->DispatchMouseEvent(event, event_type, event.click_count);
 
+  // Event handlers may remove element.
+  if (!element_)
+    return;
+
   // Create click events
   if (event_type == EventTypeNames::mouseup) {
     element_->DispatchMouseEvent(event, EventTypeNames::click,