LO Personalization not working in Linux Mint 18

I use LO in Both Windows 10 and Linux Mint in a dual-boot installation on the same PC. Since upgrading Mint to version 18 by a fresh install, LO Personalization by clicking the ‘Own Theme’ button does not work. Clicking on the color tab, then typing White in the search field results in the message ‘Searching please wait’ but after a two seconds a ‘No results found’ message appears.
Any suggestions for a remedy will be much appreciated.

I bypass the Personalisation option for changing in-house Personas as it doesn’t seem to do what I need.

If you are confident in changing the configuration, you can change the Personas using the expert configuration. You will find this in Linux-Mint LibreOffice under TOOLS > OPTIONS > ADVANCED > OPEN EXPERT CONFIGURATION.

Search for Persona not Personas. You will find two MISC settings Persona and PersonaSettings. You can edit these string settings.
Persona should be set to own
and PersonaSetttings should be set to your individual Personas Folder and header and footer files found in the user/gallery/personas folder. For example in my Default-Personas
Where the first # point to the text #rrggbb colour. #ff0000 is plain red in this case. The second colour setting is ignored.
You may then normally need to restart LibO for the settings to take effect. LibO 5.2 on my system seems to allow you to change the header and footer without a restart.

You may find bug https://bugs.documentfoundation.org/show_bug.cgi?id=59611 of interest.

Many thanks for your detailed reply.
I was about to implement your suggestion when Update Manager alerted that an that an upgrade for LO was available after I changed the ppa to get the latest LO version. To my delight, the upgrade works fine and now permits the choice of entering the URL of a Firefox theme as was possible in earlier versions of LO. Nice one LO.
I love LO and much appreciate the efforts of the developers.
Thank you again for your help. Go Linux!