Bug 132905. Wallpaper to avoid crash when we can't find a match. r=rjc, sr=alecf.

content/xul/templates/src/nsXULContentBuilder.cpp

@@ -1360,7 +1360,7 @@ nsXULContentBuilder::CreateTemplateContents(nsIContent* aElement,
     nsCOMPtr<nsIRDFResource> resource;
 
     nsCOMPtr<nsIContent> element = aElement;
-    while (1) {
+    while (element) {
         nsXULContentUtils::GetElementRefResource(element, getter_AddRefs(resource));
         if (resource)
             break;
@@ -1369,15 +1369,18 @@ nsXULContentBuilder::CreateTemplateContents(nsIContent* aElement,
         element->GetParent(*getter_AddRefs(parent));
 
         element = parent;
-
-        NS_ASSERTION(element != nsnull,
-                     "walked to the root of the content model without finding template root");
     }
 
+    NS_ASSERTION(element != nsnull, "walked off the top of the content tree");
+    if (! element)
+        return NS_ERROR_FAILURE;
+
     nsTemplateMatch* match = nsnull;
     mContentSupportMap.Get(element, &match);
 
     NS_ASSERTION(match != nsnull, "no match in the content support map");
+    if (! match)
+        return NS_ERROR_FAILURE;
 
     rv = BuildContentFromTemplate(aTemplateElement, aElement, aElement, PR_FALSE, resource, PR_FALSE,
                                   match, aContainer, aNewIndexInContainer);