Cannot enter a charge-back customer in a bill

[Raphael Mankin]

raph@W500:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.5 LTS
Release: 14.04
Codename: trusty

Gnucash 2.6.1

I have created a bill for an expense that is to be charged to a customer. I have marked the item as billable in the detail line. However I cannot enter any data in the 'Chargeback customer' field. It does not accept any input. Clicking 'edit' does not help.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: gnucash 1:2.6.1-2
ProcVersionSignature: Ubuntu 4.4.0-36.55~14.04.1-generic 4.4.16
Uname: Linux 4.4.0-36-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
CurrentDesktop: XFCE
Date: Wed Sep 21 21:59:36 2016
InstallationDate: Installed on 2016-08-07 (44 days ago)
InstallationMedia: Xubuntu 14.04.5 LTS "Trusty Tahr" - Release amd64 (20160803)
SourcePackage: gnucash
UpgradeStatus: No upgrade log present (probably fresh install)