Storage used not determined

[steffanson]

On the "about page" there's a line which reads: Used storage: ? bytes

I tested with a new created profile, where I only installed uMatrix 1.2.0.
The debugger reports no error. Please let me how I can help you at debugging this issue.

Version

Kubuntu 17.10
Firefox 57.0.4
uMatrix 1.2.0

[gorhill]

Browser bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1385832