Fixed compilation errors for gcc@linux (not all yet).

git-svn-id: svn://svn.code.sf.net/p/magicseteditor/code/trunk@181 0fc631ac-6414-0410-93d0-97cfa31319b6

src/util/action_stack.hpp

@@ -48,6 +48,7 @@ class Action {
 /// Base class/interface for objects that listen to actions
 class ActionListener {
   public:
+	virtual ~ActionListener() {}
 	/// Notification that an action a has been performed or undone
 	virtual void onAction(const Action& a, bool undone) = 0;
 };