wrong non-numeric default setting causes pages to crash with error HTTP 500

Problem/Motivation

A crashing oversight in a Fusion Accelerator module default setting crashes Fusion themed pages, therefore it must be corrected immediately after install!

Steps to reproduce

Install Fusion base theme.
Install Fusion Accelerator module and enable all its features.
Assign a Fusion theme to site pages.
a) all public pages return error page not working, HTTP 500, and
b) each theme's administrative page reloads blank with error after saving configuration (but fortunately they reopen from toolbar > Appearance > tab: Settings > ).

Proposed resolution

Immediately after installing and enabling Fusion Accelerator module, set this parameter to a correct numeric value:
toolbar > Appearance > tab: Settings > > vertical tab: Layout: Mobile > Grid width: set a numeric value, such as 360! (default incorrect not numeric value: mobile)

Remaining tasks

Correct the defaut value to a numeric value.