core: Pass NULL error in dump_impl()

If mac_selinux_access_check() or bus_verify_bypass_dump_ratelimit_async()
fail, we goto "ratelimited" where we set a custom D-BUS error. In
"ratelimited", we call sd_bus_error_setf() which eventually hits an
assert_return(!bus_error_is_dirty()). Avoid hitting this assertion by
passing NULL as the error to mac_selinux_access_check() and
bus_verify_bypass_dump_ratelimit_async() since we will override the error
immediately anyway if either fails.

We modify both functions as well to allow passing a NULL error and fix
the argument name as well while we're at it.

src/core/dbus-manager.c

@@ -1405,11 +1405,11 @@ static int dump_impl(
                  * operations, and can cause PID1 to stall. So it seems similar enough in terms of security
                  * considerations and impact, and thus use the same access check for dumps which, given the
                  * large amount of data to fetch, can stall PID1 for quite some time. */
-                r = mac_selinux_access_check(message, "reload", error);
+                r = mac_selinux_access_check(message, "reload", /* error = */ NULL);
                 if (r < 0)
                         goto ratelimited;
 
-                r = bus_verify_bypass_dump_ratelimit_async(m, message, error);
+                r = bus_verify_bypass_dump_ratelimit_async(m, message, /* error = */ NULL);
                 if (r < 0)
                         goto ratelimited;
                 if (r == 0)

src/core/selinux-access.c

@@ -193,7 +193,6 @@ int mac_selinux_access_check_internal(
         assert(message);
         assert(permission);
         assert(function);
-        assert(error);
 
         r = access_init(error);
         if (r <= 0)