wallet: remove edgecase around transaction checks

we don't populate the tx item when we're running a transaction check
from deep chain (prior to a chain replay)

lightningd/peer_control.c

@@ -990,7 +990,7 @@ static enum watch_result funding_depth_cb(struct lightningd *ld,
 	struct short_channel_id scid;
 
 	/* Sanity check */
-	if (tx && !check_funding_tx(tx, channel)) {
+	if (!check_funding_tx(tx, channel)) {
 		channel_internal_error(channel, "Bad tx %s: %s",
 				       type_to_string(tmpctx,
 						      struct bitcoin_txid, txid),

lightningd/watch.c

@@ -300,8 +300,12 @@ void watch_topology_changed(struct chain_topology *topo)
 			u32 depth;
 
 			depth = get_tx_depth(topo, &w->txid);
-			if (depth)
+			if (depth) {
+				if (!w->tx)
+					w->tx = wallet_transaction_get(w, topo->ld->wallet,
+								       &w->txid);
 				needs_rerun |= txw_fire(w, &w->txid, depth);
+			}
 		}
 	} while (needs_rerun);
 }

wallet/wallet.c

@@ -3127,6 +3127,29 @@ bool wallet_transaction_type(struct wallet *w, const struct bitcoin_txid *txid,
 	return true;
 }
 
+struct bitcoin_tx *wallet_transaction_get(const tal_t *ctx, struct wallet *w,
+					  const struct bitcoin_txid *txid)
+{
+	struct bitcoin_tx *tx;
+	struct db_stmt *stmt = db_prepare_v2(
+	    w->db, SQL("SELECT rawtx FROM transactions WHERE id=?"));
+	db_bind_txid(stmt, 0, txid);
+	db_query_prepared(stmt);
+
+	if (!db_step(stmt)) {
+		tal_free(stmt);
+		return NULL;
+	}
+
+	if (!db_column_is_null(stmt, 0))
+		tx = db_column_tx(ctx, stmt, 0);
+	else
+		tx = NULL;
+
+	tal_free(stmt);
+	return tx;
+}
+
 u32 wallet_transaction_height(struct wallet *w, const struct bitcoin_txid *txid)
 {
 	u32 blockheight;

wallet/wallet.h

@@ -1121,6 +1121,15 @@ void wallet_transaction_annotate(struct wallet *w,
 bool wallet_transaction_type(struct wallet *w, const struct bitcoin_txid *txid,
 			     enum wallet_tx_type *type);
 
+/**
+ * Get the transaction from the database
+ *
+ * Looks up a transaction we have in the database and returns it, or NULL if
+ * not found.
+ */
+struct bitcoin_tx *wallet_transaction_get(const tal_t *ctx, struct wallet *w,
+					  const struct bitcoin_txid *txid);
+
 /**
  * Get the confirmation height of a transaction we are watching by its
  * txid. Returns 0 if the transaction was not part of any block.