modules/presence_xml: fixed issue with parsing some pres-rules documents

- pres-rules that contain external links in a <conditions /> node don't
  have to have <identity /> nodes in the <conditions /> node.
- Kamailio returns an error when it finds a <conditions /> node with
  no <identity /> node inside it.
- Kamailio doesn't support external links, but it should skip over
  the <conditions /> nodes that contain them rather than return
  an error as later <conditions /> nodes may contain entries it can
  work with.

modules/presence_xml/xcap_auth.c

@@ -308,8 +308,8 @@ xmlNodePtr get_rule_node(subs_t* subs, xmlDocPtr xcap_tree )
 		identity_node = xmlNodeGetChildByName(cond_node, "identity");
 		if(identity_node == NULL)
 		{
-			LM_ERR("didn't find identity tag\n");
-			goto error;
+			LM_WARN("didn't find identity tag\n");
+			continue;
 		}	
 		
 		iden_child= xmlNodeGetChildByName(identity_node, "one");