RadGridView is throwing exception when loading layout that contains a GroupDescriptor with predefined Format with Aggregate function.

Steps to reproduce:

1. Add GroupDescriptor:
        Dim descriptor As New GroupDescriptor
        descriptor.GroupNames.Add("column3", System.ComponentModel.ListSortDirection.Ascending)
        descriptor.Aggregates.Add("Sum(column3)")
        descriptor.Format = "{0}: {1} Total montant : {2:c2}"
        Me.RadGridView1.GroupDescriptors.Add(descriptor)
2. Save Layout
3. Load Layout