wallet: Correctly handle forwards when channels or htlcs are deleted

The left join should make sure we still get the results but
referencing the fields and/or attempting to write them to the JSON-RPC
result will cause unforeseen problems. So just omit if we forgot
something.

lightningd/peer_htlcs.c

@@ -1880,6 +1880,7 @@ static void listforwardings_add_forwardings(struct json_result *response, struct
 	for (size_t i=0; i<tal_count(forwardings); i++) {
 		const struct forwarding *cur = &forwardings[i];
 		json_object_start(response, NULL);
+
 		json_add_short_channel_id(response, "in_channel", &cur->channel_in);
 		json_add_short_channel_id(response, "out_channel", &cur->channel_out);
 		json_add_num(response, "in_msatoshi", cur->msatoshi_in);

wallet/wallet.c

@@ -2481,9 +2481,16 @@ const struct forwarding *wallet_forwarded_payments_get(struct wallet *w,
 		cur->msatoshi_in = sqlite3_column_int64(stmt, 1);
 		cur->msatoshi_out = sqlite3_column_int64(stmt, 2);
 		cur->fee = cur->msatoshi_in - cur->msatoshi_out;
-		sqlite3_column_sha256_double(stmt, 3, &cur->payment_hash);
-		sqlite3_column_short_channel_id(stmt, 4, &cur->channel_in);
-		sqlite3_column_short_channel_id(stmt, 5, &cur->channel_out);
+
+		if (sqlite3_column_type(stmt, 3) != SQLITE_NULL) {
+			cur->payment_hash = tal(ctx, struct sha256_double);
+			sqlite3_column_sha256_double(stmt, 3, cur->payment_hash);
+		} else {
+			cur->payment_hash = NULL;
+		}
+
+		cur->channel_in.u64 = sqlite3_column_int64(stmt, 4);
+		cur->channel_out.u64 = sqlite3_column_int64(stmt, 5);
 	}
 
 	db_stmt_done(stmt);

wallet/wallet.h

@@ -162,7 +162,7 @@ static inline const char* forward_status_name(enum forward_status status)
 struct forwarding {
 	struct short_channel_id channel_in, channel_out;
 	u64 msatoshi_in, msatoshi_out, fee;
-	struct sha256_double payment_hash;
+	struct sha256_double *payment_hash;
 	enum forward_status status;
 };