Fix templating of tailscale_args_string if tailscale_tags is an empty list

[UnholyRope]

tailscale_tags_string templated to None, which is not a valid argument.

It would template to something like "--login-server=https://ts.example.com None --timeout=120s", with None being an invalid argument causing the following error:

fatal: [host]: FAILED! => {"ansible_job_id": "j1.1", "changed": true, "cmd": ["tailscale", "up", "--login-server=https://ts.example.com", "None", "--timeout=120s", "--authkey=1234"], "delta": "0:00:00.004653", "end": "2024-09-19 12:59:36.991005", "finished": 1, "msg": "non-zero return code", "rc": 1, "results_file": "/root/.ansible_async/j1.1", "start": "2024-09-19 12:59:36.986352", "started": 1, "stderr": "too many non-flag arguments: [\"None\" \"--timeout=120s\" \"--auth-key=1234\"]", "stderr_lines": ["too many non-flag arguments: [\"None\" \"--timeout=120s\" \"--auth-key=1234\"]"], "stdout": "", "stdout_lines": []}

This seems to be an issue since v4.4.0.