Main loop panics due to Stream being an option

Relevant backtrace:

  18:     0x5633f8860e7a - core::option::Option<T>::expect::h8b8d014b889440d7
                               at /rustc/4b91a6ea7258a947e59c6522cd5898e7c0a6a88f/library/core/src/option.rs:738:21
  19:     0x5633f887d139 - pipewire::stream::ListenerLocalCallbacks<D>::into_raw::on_process::h07ed14a339933cdd
                               at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/pipewire-0.5.0/src/stream.rs:489:34
  20:     0x7f1f22ff46a8 - <unknown>
  21:     0x7f1f2296e769 - <unknown>
  22:     0x7f1f2296d8aa - <unknown>
  23:     0x7f1f2296ee33 - <unknown>
  24:     0x7f1f22fd1479 - pw_main_loop_run
  25:     0x5633f8b9c89e - pipewire::main_loop::MainLoopInner::run::h1a8f544d41fb5830
                               at ~/.cargo/registry/src/github.com-1ecc6299db9ec823/pipewire-0.5.0/src/main_loop.rs:86:13