Fix condition for handling "Last set from {path}"

:h :verbose-cmd

When 'verbose' is non-zero, listing the value of a Vim option or a key map or
an abbreviation or a user-defined function or a command or a highlight group
or an autocommand will also display where it was last defined.
Modify handling redir highlight

Set &verbose value to 0 temporarily to avoid the highlight variable contain
"Last set from {path}"
Merge pull request #11 from haya14busa/support/test

Fix condition for handling "Last set from {path}"