Detect programmer error in delegate usage as early as possible and fail.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5223 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/crowd/client/PlaceController.java

@@ -222,6 +222,7 @@ public abstract class PlaceController extends Controller
      */
     protected void addDelegate (PlaceControllerDelegate delegate)
     {
+        ratifyDelegate(delegate);
         if (_delegates == null) {
             _delegates = new ArrayList<PlaceControllerDelegate>();
         }
@@ -266,6 +267,14 @@ public abstract class PlaceController extends Controller
         }
     }
 
+    /**
+     * Protects against programmer error.
+     */
+    protected void ratifyDelegate (PlaceControllerDelegate delegate)
+    {
+        // nothing to do here, all PlaceControllerDelegates are safe for us
+    }
+
     /** A reference to the active client context. */
     protected CrowdContext _ctx;