Don't NPE when we have a missing color class in the list, instead, return -1 to emulate the old IntIntMap behavior.

git-svn-id: svn+ssh://src.earth.threerings.net/vilya/trunk@926 c613c5cb-e716-0410-b11b-feb51c14d237

src/java/com/threerings/stage/data/StageSceneModel.java

@@ -53,7 +53,10 @@ public class StageSceneModel extends SceneModel
     public int getDefaultColor (int classId)
     {
         if (defaultColors != null) {
-            return defaultColors.get(classId);
+            Integer result = defaultColors.get(classId);
+            if (result != null) {
+                return result;
+            }
         }
         return -1;
     }