diff -urN ntop-5.0.orig/httpd.c ntop-5.0/httpd.c
--- ntop-5.0.orig/httpd.c	2012-07-18 01:14:33.000000000 +0200
+++ ntop-5.0/httpd.c	2012-07-20 12:15:57.306231889 +0200
@@ -3321,6 +3321,9 @@
     strncpy(thePw, &outBuffer[i+1], thePwLen-1)[thePwLen-1] = '\0';
   }
 
+  if(user == NULL)
+    user = "";
+
   if(strlen(user) >= sizeof(theHttpUser)) user[sizeof(theHttpUser)-1] = '\0';
   strcpy(theHttpUser, user);