Fix failure if username of patch uploader is empty
Fix failure if username of patch uploader is empty

Uploader.username field may be empty if the patch is created
from a email unknown to gerrit.

Change-Id: If9b740a42c01a6a3a6feef448b574adfca61acc5

danielmellado/stackalytics,mhharsh/stackalytics,mohitsethi/stackalytics,AlexanderYAPPO/stackalytics,stackforge/stackalytics,mhharsh/stackalytics,0xf2/stackalytics,stackforge/stackalytics,dliu2015/stackalytics_zanata,Code-Fly/stackalytics,dliu2015/stackalytics_zanata,Solinea/stackalytics,Solinea/stackalytics,Code-Fly/stackalytics,openstack/stackalytics,AlexanderYAPPO/stackalytics,0xf2/stackalytics,mhharsh/stackalytics,0xf2/stackalytics,danielmellado/stackalytics,Mirantis/stackalytics,nihilifer/stackalytics,Mirantis/stackalytics,Mirantis/stackalytics,nihilifer/stackalytics,dliu2015/stackalytics_zanata,danielmellado/stackalytics,0xf2/stackalytics,stackforge/stackalytics,openstack/stackalytics,Code-Fly/stackalytics,Solinea/stackalytics,mohitsethi/stackalytics,openstack/stackalytics,mohitsethi/stackalytics,openstack/stackalytics,nihilifer/stackalytics,AlexanderYAPPO/stackalytics