Fix review nit

xpcom/ds/nsCRT.h

@@ -196,6 +196,7 @@ public:
   static char* strtok(char* str, const char* delims, char* *newStr); 
 
   static PRUint32 strlen(const PRUnichar* s) {
+    // XXXbsmedberg: remove this null-check at some point
     if (!s) {
       NS_ERROR("Passing null to nsCRT::strlen");
       return 0;