add null ptr check to stop crash seen in talkback

layout/base/nsFrameManager.cpp

@@ -739,10 +739,15 @@ FrameManager::DequeuePostedEventFor(nsIFrame* aFrame)
 }
 
 void
-FrameManager::HandlePLEvent(CantRenderReplacedElementEvent* aEvent)
-{
+FrameManager::HandlePLEvent(CantRenderReplacedElementEvent* aEvent) {
+
   FrameManager* frameManager = (FrameManager*)aEvent->owner;
 
+    //adding a ptr check since talkback is complaining about a crash here.
+    //I suspect that if the event->owner is really null, bad things will happen
+    //elsewhere.
+  if(frameManager) { 
+  
     // Remove the posted event from the linked list
     CantRenderReplacedElementEvent** events = &frameManager->mPostedEvents;
     while (*events) {
@@ -761,6 +766,7 @@ FrameManager::HandlePLEvent(CantRenderReplacedElementEvent* aEvent)
     frameManager->mPresShell->GetPresContext(getter_AddRefs(presContext));
     frameManager->mStyleSet->CantRenderReplacedElement(presContext, aEvent->mFrame);    
     frameManager->mPresShell->ExitReflowLock(PR_TRUE);
+  }
 }
 
 void

layout/html/base/src/nsFrameManager.cpp

@@ -739,10 +739,15 @@ FrameManager::DequeuePostedEventFor(nsIFrame* aFrame)
 }
 
 void
-FrameManager::HandlePLEvent(CantRenderReplacedElementEvent* aEvent)
-{
+FrameManager::HandlePLEvent(CantRenderReplacedElementEvent* aEvent) {
+
   FrameManager* frameManager = (FrameManager*)aEvent->owner;
 
+    //adding a ptr check since talkback is complaining about a crash here.
+    //I suspect that if the event->owner is really null, bad things will happen
+    //elsewhere.
+  if(frameManager) { 
+  
     // Remove the posted event from the linked list
     CantRenderReplacedElementEvent** events = &frameManager->mPostedEvents;
     while (*events) {
@@ -761,6 +766,7 @@ FrameManager::HandlePLEvent(CantRenderReplacedElementEvent* aEvent)
     frameManager->mPresShell->GetPresContext(getter_AddRefs(presContext));
     frameManager->mStyleSet->CantRenderReplacedElement(presContext, aEvent->mFrame);    
     frameManager->mPresShell->ExitReflowLock(PR_TRUE);
+  }
 }
 
 void