Except empty module_groups
Except empty module_groups

module_groups seems expected as empty on the code, but the extracting
code specified actual keys(like 'openstack') in process_project_list().
This patch changes the method for an empty module_groups.

NOTE: This code becomes necessary to use stackalytics locally.

Change-Id: I8791829e5d6811a2d661a222eee5d95937c155fb

0xf2/stackalytics,openstack/stackalytics,openstack/stackalytics,0xf2/stackalytics,0xf2/stackalytics,openstack/stackalytics,openstack/stackalytics,0xf2/stackalytics,stackforge/stackalytics,stackforge/stackalytics,stackforge/stackalytics