AbstractModuleNoTrait's use of glob() must handle false return value

The glob() function we use for finding config files can return "false" on some platforms instead of an empty array when no files are found. This was causing an error in the foreach statement on these platforms. False is now transformed to an empty array to avoid this.

Note that glob() also returns "false" in an error case - unfortunately this does mean we can't tell the difference between no files found and an error in the glob() function.  In either case we treat it as if no files were found.