fix bug where "follow" failed for empty users (who followed no one)

src/twister.cpp

@@ -1595,9 +1595,8 @@ Value follow(const Array& params, bool fHelp)
         string username = users[u].get_str();
         torrent_handle h = startTorrentUser(username);
 
+        if( h.is_valid() ) {
             LOCK(cs_twister);
-        if( h.is_valid() && m_users.count(localUser) &&
-            !m_users[localUser].m_following.count(username) ) {
             m_users[localUser].m_following.insert(username);
         }
     }