fix: fix falsy logic to check if the operation has a explicit transaction being used

Author: RodolfoFerreira

RepoDb.Extensions/RepoDb.PostgreSql.BulkOperations/RepoDb.PostgreSql.BulkOperations/Extensions/NpgsqlWrapper.cs

@@ -269,7 +269,7 @@ private static TResult TransactionalExecute<TResult>(this NpgsqlConnection conne
         {
             // Variables
             var result = default(TResult);
-            var hasTransaction = (transaction == null || Transaction.Current != null);
+            var hasTransaction = (transaction != null || Transaction.Current != null);
 
             // Open
             connection.EnsureOpen();
@@ -334,7 +334,7 @@ private static async Task<TResult> TransactionalExecuteAsync<TResult>(this Npgsq
         {
             // Variables
             var result = default(TResult);
-            var hasTransaction = (transaction == null || Transaction.Current != null);
+            var hasTransaction = (transaction != null || Transaction.Current != null);
 
             // Open
             await connection.EnsureOpenAsync(cancellationToken);