Ensure that 'run' has at least one argument for the command

Otherwise, it would lead to:
  $ toolbox run
  /usr/bin/toolbox: line 1287: shift: 4: shift count out of range
  toolbox: command '' not found in container fedora-toolbox-31

Fallout from 2da4cc4634

https://github.com/containers/toolbox/pull/332

toolbox

@@ -2533,6 +2533,7 @@ case $op in
             esac
             shift
         done
+        exit_if_missing_argument "$op" "$1"
         if ! update_container_and_image_names; then
             exit 1
         fi