Fix detection of having no packages

Sometimes empty elements containing only spaces are pushed in to the
packages array, before the code would only detect that there are no
pacakges to install when only one spaces was inserted, now it should
work for any arbitrary count of elements containing only spaces.

zypper_autoremove.bash

@@ -13,7 +13,7 @@ done < <(echo "$package_list" | tail -n+$((table_start+2)))
 
 unneeded_package_list=$(printf '%s ' "${unneeded_packages[@]}")
 
-if [ ! "$unneeded_package_list" = " " ]; then
+if [ -n "$(echo $unneeded_package_list | tr -d ' ')" ]; then
     sudo zypper rm -u $unneeded_package_list
 else
     echo "No unneeded packages."