transport-helper: fix memory leak of helper on disconnect

transport-helper: fix memory leak of helper on disconnect

disconnect_helper() only frees data inside of the if(data->helper) block
[1]. When the transport is disconnected without the helper being fully
started, data->name allocated in transport_helper_init()
is never freed.

Move FREE_AND_NULL(data->name) outside the conditional block so it's
always freed on disconnect.

[1]: https://lore.kernel.org/git/05fbadbae2184479c87c37675dde7bd79b3e32ab.1716465556.git.ps@pks.im/

Mentored-by: Karthik Nayak <redacted>
Mentored-by: Chandra Pratap <redacted>
Signed-off-by: Pablo Sabater <redacted>
Signed-off-by: Junio C Hamano <redacted>