partial fix for bug #364298: Crash [ @ BindStatementURI ] when pasting a folder from the history sidebar into the bookmarks toolbar

this turns the crash into a javascript exception, but we are still unable to copy and paste history folder into bookmarks.

r=dietrich

toolkit/components/places/src/nsNavHistory.cpp

@@ -4756,6 +4756,8 @@ void GetSubstringFromNthDot(const nsCString& aInput, PRInt32 aStartingSpot,
 nsresult BindStatementURI(mozIStorageStatement* statement, PRInt32 index,
                           nsIURI* aURI)
 {
+  NS_ENSURE_ARG_POINTER(aURI);
+
   nsCAutoString utf8URISpec;
   nsresult rv = aURI->GetSpec(utf8URISpec);
   NS_ENSURE_SUCCESS(rv, rv);