diff -r 3f794789df0e -r 8bf60e7a6b6c Admin/mira.py
--- a/Admin/mira.py	Wed Dec 19 10:51:46 2012 +0100
+++ b/Admin/mira.py	Wed Dec 19 11:10:47 2012 +0100
@@ -87,6 +87,9 @@
 def extract_image_size(isabelle_home):
     
     isabelle_output = isabelle_getenv(isabelle_home, 'ISABELLE_OUTPUT')
+    if not path.exists(isabelle_output):
+        return {}
+
     return dict((p, path.getsize(path.join(isabelle_output, p))) for p in os.listdir(isabelle_output) if p != "log")
 
 def extract_report_data(isabelle_home, logdata):