[#6531] Fixed anonymous comments in trac ticket export

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
diff --git a/Allura/allura/scripts/trac_export.py b/Allura/allura/scripts/trac_export.py
index 4d908bc..43462df 100644
--- a/Allura/allura/scripts/trac_export.py
+++ b/Allura/allura/scripts/trac_export.py
@@ -155,7 +155,7 @@
         res = []
         for comment in d['entries']:
             c = {}
-            c['submitter'] = comment.author
+            c['submitter'] = getattr(comment, 'author', None)
             c['date'] = comment.updated_parsed
             c['comment'] = html2text(comment.summary)
             c['class'] = 'COMMENT'