Cycle through windows of the same application using wmcrtl

I've found a problem in the script, if no window has focus.

May you try the following modified script:

#!/bin/bash
win_class=$1 # 'terminator' # $1

# get list of all windows matching with the class above
win_list=$(wmctrl -x -l | grep -i $win_class | awk '{print $1}' )

# get id of the focused window
active_win_id=$(xprop -root | grep '^_NET_ACTIVE_W' | awk -F'# 0x' '{print $2}')
if [ "$active_win_id" == "0" ]; then
    active_win_id=""
fi

# get next window to focus on, removing id active
switch_to=$(echo $win_list | sed s/.*$active_win_id// | awk '{print $1}')

# if the current window is the last in the list ... take the first one
if [ "$switch_to" == '' ];then
   switch_to=$(echo $win_list | awk '{print $1}')
fi

# switch to window
wmctrl -i -a $switch_to