Issue navigator should be able to sort on 'Σ Remaining Estimate' column

I use the 'Σ Remaining Estimate' in your issue navigator instead of the default 'Remaining Estimate' so I have an idea of the estimates in tasks and subtasks. However, you can not sort on that column. I want to sort to be able to see the issues that have no estimates on them or a remaining estimate of 0 minutes (since you cannot define a search filter for this, unless I overlooked something).