Don't assume mRootContent is non-null. Bug 340796, r=sicking, sr=neil, branch181=sicking

content/xul/document/src/nsXULDocument.cpp

@@ -1351,7 +1351,8 @@ nsXULDocument::GetPixelDimensions(nsIPresShell* aShell, PRInt32* aWidth,
 
     FlushPendingNotifications(Flush_Layout);
 
-    nsIFrame* frame = aShell->GetPrimaryFrameFor(mRootContent);
+    nsIFrame* frame =
+        mRootContent ? aShell->GetPrimaryFrameFor(mRootContent) : nsnull;
     if (frame) {
         nsIView* view = frame->GetView();
         // If we have a view check if it's scrollable. If not,
@@ -2867,7 +2868,10 @@ nsXULDocument::ResumeWalk()
         mDocumentLoaded = PR_TRUE;
 
         nsAutoString title;
-        mRootContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::title, title);
+        if (mRootContent) {
+            mRootContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::title,
+                                  title);
+        }
         SetTitle(title);
 
         StartLayout();
@@ -3546,6 +3550,10 @@ nsXULDocument::OverlayForwardReference::Resolve()
     mOverlay->GetAttr(kNameSpaceID_None, nsXULAtoms::id, id);
     if (id.IsEmpty()) {
         // overlay had no id, use the root element
+        if (!mDocument->mRootContent) {
+            return eResolve_Error;
+        }
+        
         mDocument->InsertElement(mDocument->mRootContent, mOverlay, notify);
         mResolved = PR_TRUE;
         return eResolve_Succeeded;