Fix conflict check

[Arteiii]

Currently the

# If `--mode` occurs in args and `INPUT_CHECKBOX` is set, exit with an error 
# Use `--mode` instead of `--mode task` to ensure that the checkbox is not getting overwritten
if [[ "$ARGS" =~ "--mode" ]] && [ -n "${INPUT_CHECKBOX:-}" ]; then
  echo "Error: '--mode' is set in args but 'checkbox' is set in the action configuration. Please remove one of them to avoid conflicts."
  exit 1
fi

checks if the checkbox has a value and not if it's true or false resulting in always true...

[mre]

Oh. Would you like to create a PR for that?