PHP error upon install

I did a fresh Joomla install on localhost. Downloaded & installed the latest Solidres version (10 minutes ago...)

Upon checking in the front end I get this error message:
See the attached screen.

I can hide the error in the control panel. Is this a serious error?

Hi,

This error will disappear if you re-save your room type, it is also a minor notice, nothing serious.

Regards,