How to handle an empty argument in a function?

Question

bash

I am writing a backup script.
It has a function using tar to make an archive.
There are 3 types of archives. Two of them have excluded folders. One does not.
Paths to be archived and excluded folders are passed using array references from the main script.
The problem is that in the third option, when there are no excluded folders, the script is interrupted.
The output of bash -x shows that an empty string is being added to tar, which I understand is the reason. Tell me how to fix this?
Script example:

#!/bin/bash
function backup() {
    local include=("${!1}")
  local exclude=("${!2}")
    tar -cvpzPf /home/backup/backup.tar.gz "${include[@]}" "${exclude[@]}"
}

case "$1" in
    1)
        include=(/foo2 /foo3)
        exclude=(/bar2 /bar3)
        backup include[@] exclude[@]
    ;;
    2)
        include=(/foo /foo1)
        exclude=(/bar /bar1)
        backup include[@] exclude[@]
    ;;
    3)
        include=(/etc /sbin)
        backup include[@]
    ;;
esac

The example is schematic, but shows the general essence

Answer 1

Check the lengths of the local_include and local_exclude lines and form one line from them, which is slipped into tar