Otherwise:
```
Feb 19 16:35:34 localhost systemd-gpt-auto-generator[188]: Assertion 's' failed at src/shared/image-policy.c:656, function parse_image_policy_argument(). Aborting.
```
Fixes
06e78680e3c36589b785f90ecda64d124905a3f7
else if (streq(key, "ro") && !value)
arg_root_rw = false;
else if (proc_cmdline_key_streq(key, "systemd.image_policy"))
- return parse_image_policy_argument(optarg, &arg_image_policy);
+ return parse_image_policy_argument(value, &arg_image_policy);
else if (streq(key, "systemd.swap")) {