Check the grid exists before trying to remove weight when removing items.

build-snapshot.sh

@@ -1,6 +1,6 @@
 VERSION=0.63
 DATE=`date +%Y%m%d`
-RELEASE=2.77
+RELEASE=2.78
 TARBALL=sugar-$VERSION-$RELEASE.${DATE}git.tar.bz2
 
 rm sugar-$VERSION.tar.bz2

sugar/graphics/spreadbox.py

@@ -114,7 +114,8 @@ class SpreadBox(hippo.CanvasBox, hippo.CanvasItem):
 
     def remove_item(self, item):
         info = item.get_data('item-info')
-        info.remove_weight(self._grid)
+        if self._grid:
+            info.remove_weight(self._grid)
         
         self.remove(item)