Add member to Security Group 500 Error

To use the option security group, you need to enable in the company plan the max amount of security groups.

We can create a security group, but when trying to add a member to this group, we get the error 500

Value cannot be null. Parameter name: second

In the log file :

2015-12-16 15:24:21,833 ::: [32] ERROR ::: CloudPanel.Modules.SecurityGroupModule — Error updating security group for Test: System.ArgumentNullException: Value cannot be null.
Parameter name: second
at System.Linq.Enumerable.Except[TSource](IEnumerable1 first, IEnumerable1 second)
at CloudPanel.Modules.SecurityGroupModule.<.ctor>b__1_17(Object _)

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