Clock panel plugin keeps losing formatting

[Danny Howard]

Any time I adjust the properties in the Clock panel plugin, the clock will "disappear" (null format) from the Panel.

The only way I can keep the clock to appear after adjusting properties is to:
Clock Options Format: Custom Format
* required: *touch* the custom format string, else the format string gets wiped out upon closing the dialog

Current workaruond: any time I touch Clock properties, I manually enter a custom format like %H:%M:%S or if the format string is present I have to click on the text field so that the properties dialog will store the incumbent value instead of wiping it out.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xfce4-panel 4.12.0-3ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-92.115-generic 4.4.76
Uname: Linux 4.4.0-92-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu Aug 24 12:27:09 2017
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-trusty-amd64-osp1-20150720-0
EcryptfsInUse: Yes
InstallationDate: Installed on 2016-10-14 (314 days ago)
InstallationMedia: Ubuntu 14.04 "Trusty" - Build amd64 LIVE Binary 20150720-04:06
SourcePackage: xfce4-panel
UpgradeStatus: Upgraded to xenial on 2016-10-14 (314 days ago)