Fix crash in DHCPINFORM without valid --dhcp-range.

CHANGELOG

@@ -51,6 +51,10 @@ version 2.61
 	    the lo interface. Thanks to Mathieu Trudel-Lapierre for
 	    the idea and initial patch. 
 
+	    Fix crash, introduced in 2.60, when a DHCPINFORM is
+	    received from a network which has no valid dhcp-range.
+	    Thanks to Stephane Glondu for the bug report.
+
  
 version 2.60
             Fix compilation problem in Mac OS X Lion. Thanks to Olaf

src/rfc2131.c

@@ -2095,6 +2095,7 @@ static void do_options(struct dhcp_context *context,
   struct dhcp_netid_list *id_list;
 
   /* filter options based on tags, those we want get DHOPT_TAGOK bit set */
+  if (context)
     context->netid.next = NULL;
   tagif = option_filter(netid, context && context->netid.net ? &context->netid : NULL, config_opts);