cookie: get_top_domain() sets zero length for null domains

This silents a compilation warning with gcc -O3.

Author: monnerat

lib/cookie.c

@@ -245,18 +245,17 @@ static bool pathmatch(const char *cookie_path, const char *request_uri)
  */
 static const char *get_top_domain(const char * const domain, size_t *outlen)
 {
-  size_t len;
+  size_t len = 0;
   const char *first = NULL, *last;
 
-  if(!domain)
-    return NULL;
-
-  len = strlen(domain);
-  last = memrchr(domain, '.', len);
-  if(last) {
-    first = memrchr(domain, '.', (last - domain));
-    if(first)
-      len -= (++first - domain);
+  if(domain) {
+    len = strlen(domain);
+    last = memrchr(domain, '.', len);
+    if(last) {
+      first = memrchr(domain, '.', (last - domain));
+      if(first)
+        len -= (++first - domain);
+    }
   }
 
   if(outlen)