Fix handling of unset AppConfig model properties.

BUG=None
R=agable@chromium.org

Review URL: https://codereview.chromium.org/23602002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/reviewbot@219790 0039d316-1c4b-4281-b951-d872f2087c98

app_config.py

diff --git a/app_config.py b/app_config.py
index 1171517..bf3a698 100644
--- a/app_config.py
+++ b/app_config.py
@@ -61,7 +61,7 @@
     for field in FIELDS:
       self.response.write(
           '<tr><td>%s</td><td><textarea name="%s">%s</textarea></td></tr>' %
-          (field, field, cgi.escape(getattr(app_config, field, ''))))
+          (field, field, cgi.escape(getattr(app_config, field) or '')))
     self.response.write('<tr><td><input type="submit" value="Set"></td></tr>')
     self.response.write('</table><form></body></body>')