Edit custom attribute dialog sometimes empty

[ghost]

[Version] 16.1 prefix7 2017/03/16

[How to reproduce]

1. create custom subscription attribute (in my case encrypted, but I do not think it matters)
2. leave browser for a few minutes (4 with me)
3. go back to and press Edit custom attribute

[Expected result] The fields are filled out to the values previously entered

[Observed result] Fields are empty (not always)

[Details] See attached logfile.