*highlight: Better code handling history expansion

Times like 181x ms seem to occur more often.

hsmw-highlight

@@ -568,7 +568,7 @@ __HSMW_HIGHLIGHT_TOKENS_TYPES=(
                  (( highlight_glob )) && style=globbing || style=default;;
         *)       if [[ $arg = $'\x7d' ]] && (( right_brace_is_recognised_everywhere )); then
                    # was handled by the $'\x7d' case above
-                 elif [[ $arg[0,1] = $histchars[0,1] ]] && (( $#arg[0,2] == 2 )); then
+                 elif [[ $arg[1] = $histchars[1] && -n "${arg[2]}" ]]; then
                    style=history-expansion
                  elif (( arg_type == 3 )); then
                    style=commandseparator