nta.c: check input in nta_leg_by_uri()

Ignore-this: f149ac04b5e1bf078c3b00e837738301

Coverity issue.

darcs-hash:20090512181707-db55f-29553eaeca4eb14796a7123463e084cf8de1a784.gz

libsofia-sip-ua/nta/nta.c

@@ -4896,7 +4896,7 @@ nta_leg_t *leg_find(nta_agent_t const *sa,
 nta_leg_t *nta_leg_by_uri(nta_agent_t const *agent, url_string_t const *us)
 {
   url_t *url;
-  nta_leg_t *leg;
+  nta_leg_t *leg = NULL;
 
   if (!agent)
     return NULL;
@@ -4906,11 +4906,11 @@ nta_leg_t *nta_leg_by_uri(nta_agent_t const *agent, url_string_t const *us)
 
   url = url_hdup(NULL, us->us_url);
 
+  if (url) {
     agent_aliases(agent, url, NULL);
-
-  leg = url ? dst_find(agent, url, NULL) : NULL;
-
+    leg = dst_find(agent, url, NULL);
     su_free(NULL, url);
+  }
 
   return leg;
 }