BUG/MINOR: h3: Missing wait event struct field initialization

BUG/MINOR: h3: Missing wait event struct field initialization

This one has been detected by valgrind:
==2179331== Conditional jump or move depends on uninitialised value(s)
==2179331==    at 0x1B6EDE: qcs_notify_recv (mux_quic.c:201)
==2179331==    by 0x1A17C5: qc_handle_uni_strm_frm (xprt_quic.c:2254)
==2179331==    by 0x1A1982: qc_handle_strm_frm (xprt_quic.c:2286)
==2179331==    by 0x1A2CDB: qc_parse_pkt_frms (xprt_quic.c:2550)
==2179331==    by 0x1A6068: qc_treat_rx_pkts (xprt_quic.c:3463)
==2179331==    by 0x1A6C3D: quic_conn_app_io_cb (xprt_quic.c:3589)
==2179331==    by 0x3AA566: run_tasks_from_lists (task.c:580)
==2179331==    by 0x3AB197: process_runnable_tasks (task.c:883)
==2179331==    by 0x357E56: run_poll_loop (haproxy.c:2750)
==2179331==    by 0x358366: run_thread_poll_loop (haproxy.c:2921)
==2179331==    by 0x3598D2: main (haproxy.c:3538)
==2179331==