psbt: dont crash when printing psbt to log

We call `tal_wally_start` and then `tal_wally_start` again in
`type_to_string` for psbt.

end the last tal before calling type to string.

Fixes: ElementsProject#5499
Reported-By: @fiatjaf

lightning_hsmd: FATAL SIGNAL 6 (version v0.11.0.1-231-gddf8fbd-modded)
0x5574ca0d87ef send_backtrace
	common/daemon.c:33
0x5574ca0d8877 crashdump
	common/daemon.c:46
0x7f76ef63e8df ???
	???:0
0x7f76ef68e36c ???
	???:0
0x7f76ef63e837 ???
	???:0
0x7f76ef628534 ???
	???:0
0x5574ca0df55e tal_wally_start
	common/utils.c:27
0x5574ca0e4024 psbt_to_b64
	bitcoin/psbt.c:687
0x5574ca0e4093 fmt_wally_psbt_
	bitcoin/psbt.c:694
0x5574ca0df4b9 type_to_string_
	common/type_to_string.c:32
0x5574ca0d5139 sign_our_inputs
	hsmd/libhsmd.c:486
0x5574ca0d5206 handle_sign_withdrawal_tx
	hsmd/libhsmd.c:1029
0x5574ca0d63c4 hsmd_handle_client_message
	hsmd/libhsmd.c:1575
0x5574ca0ce763 handle_client
	hsmd/hsmd.c:671
0x5574ca100032 next_plan
	ccan/ccan/io/io.c:59
0x5574ca1004b9 do_plan
	ccan/ccan/io/io.c:407
0x5574ca100552 io_ready
	ccan/ccan/io/io.c:417
0x5574ca101daf io_loop
	ccan/ccan/io/poll.c:453
0x5574ca0ceb7b main
	hsmd/hsmd.c:739
0x7f76ef62928f ???
	???:0
0x7f76ef629349 ???
	???:0
0x5574ca0cda04 ???
	../sysdeps/x86_64/start.S:115

hsmd/libhsmd.c

@@ -502,14 +502,16 @@ static void sign_our_inputs(struct utxo **utxos, struct wally_psbt *psbt)
 			tal_wally_start();
 			if (wally_psbt_sign(psbt, privkey.secret.data,
 					    sizeof(privkey.secret.data),
-					    EC_FLAG_GRIND_R) != WALLY_OK)
+					    EC_FLAG_GRIND_R) != WALLY_OK) {
+				tal_wally_end(psbt);
 				hsmd_status_broken(
 				    "Received wally_err attempting to "
 				    "sign utxo with key %s. PSBT: %s",
 				    type_to_string(tmpctx, struct pubkey,
 						   &pubkey),
 				    type_to_string(tmpctx, struct wally_psbt,
 						   psbt));
+			}
 			tal_wally_end(psbt);
 		}
 	}