Fix issue where RegionCombinerModule was not removing regions from its dictionary on RemoveRegion(), causing a later issue if regions were restarted (removed then readded).

OpenSim/Region/RegionCombinerModule/RegionCombinerModule.cs

@@ -84,6 +84,8 @@ namespace OpenSim.Region.RegionCombinerModule
 
         public void RemoveRegion(Scene scene)
         {
+            lock (m_startingScenes)
+                m_startingScenes.Remove(scene.RegionInfo.originRegionID);
         }
 
         public void RegionLoaded(Scene scene)