Fixed locking broken on first launch

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@7783 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/challenges/unlock_manager.cpp

@@ -200,6 +200,7 @@ void UnlockManager::load()
         save();
         
         if (root) delete root;
+        computeActive();
         return;
     }