better nil transaction checking for commits (#8787)

go/libraries/doltcore/sqle/database_provider.go

@@ -419,12 +419,15 @@ func (p *DoltDatabaseProvider) CreateDatabase(ctx *sql.Context, name string) err
 }
 
 func commitTransaction(ctx *sql.Context, dSess *dsess.DoltSession, rsc *doltdb.ReplicationStatusController) error {
+	// there is no current transaction to commit; this happens in certain tests like
 	currentTx := ctx.GetTransaction()
-
-	err := dSess.CommitTransaction(ctx, currentTx)
-	if err != nil {
-		return err
+	if currentTx != nil {
+		err := dSess.CommitTransaction(ctx, currentTx)
+		if err != nil {
+			return err
+		}
 	}
+
 	newTx, err := dSess.StartTransaction(ctx, sql.ReadWrite)
 	if err != nil {
 		return err

go/libraries/doltcore/sqle/dsess/session.go

@@ -448,11 +448,6 @@ func (d *DoltSession) CommitTransaction(ctx *sql.Context, tx sql.Transaction) (e
 		return nil
 	}
 
-	// There is no transaction to commit
-	if tx == nil {
-		return nil
-	}
-
 	dirties := d.dirtyWorkingSets()
 	if len(dirties) == 0 {
 		return nil

go/libraries/doltcore/sqle/testutil.go

@@ -103,9 +103,13 @@ func ExecuteSql(dEnv *env.DoltEnv, root doltdb.RootValue, statements string) (do
 		}
 	}
 
-	err = dsess.DSessFromSess(ctx.Session).CommitTransaction(ctx, ctx.GetTransaction())
-	if err != nil {
-		return nil, err
+	// commit leftover transaction
+	trx := ctx.GetTransaction()
+	if trx != nil {
+		err = dsess.DSessFromSess(ctx.Session).CommitTransaction(ctx, trx)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	return db.GetRoot(ctx)