=== modified file 'softwarecenter/db/pkginfo_impl/aptcache.py'
--- a/softwarecenter/db/pkginfo_impl/aptcache.py	2012-12-18 10:23:55 +0000
+++ b/softwarecenter/db/pkginfo_impl/aptcache.py	2014-04-10 09:16:32 +0000
@@ -588,10 +588,13 @@
 
     # space calculation stuff
     def _on_total_size_calculation_done(self, trans, space):
-        pkgname = trans.packages[0][0]
-        self.emit(
-            "query-total-size-on-install-done",
-            pkgname, trans.download, trans.space)
+        # ensure trans contains the data we expect, see LP: #1225885
+        if trans.packages and trans.packages[0]:
+            pkgname = trans.packages[0][0]
+            self.emit(
+                "query-total-size-on-install-done",
+                pkgname, trans.download, trans.space)
+            
 
     def _on_trans_simulate_error(self, error):
         LOG.exception("simulate failed")