Bug 1066338 - Don't error out if the queue has no message count.
Bug 1066338 - Don't error out if the queue has no message count.

markrcote/pulseguardian,markrcote/pulseguardian,mccricardo/pulseguardian,mozilla/pulseguardian,markrcote/pulseguardian,mozilla/pulseguardian,mccricardo/pulseguardian,yaoweizhen/pulseguardian,yaoweizhen/pulseguardian,mozilla/pulseguardian,mccricardo/pulseguardian,yaoweizhen/pulseguardian,mccricardo/pulseguardian,markrcote/pulseguardian,yaoweizhen/pulseguardian,mozilla/pulseguardian