Write chal;enges file when none is found

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@6684 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/challenges/unlock_manager.cpp

@@ -214,6 +214,7 @@ void UnlockManager::load()
     {
         std::cerr << "Challenge file '" << filename << "' will be created." 
                   << std::endl;
+        save();
         return;
     }