Fix NullReferenceException when Connection isn't set.

IsValid (which checks preconditions) is called after ResetCommandTimeout.

Author: bgrainger

src/MySqlConnector/MySql.Data.MySqlClient/MySqlCommand.cs

@@ -226,7 +226,7 @@ internal IDisposable RegisterCancel(CancellationToken token)
 		internal void ResetCommandTimeout()
 		{
 			var commandTimeout = CommandTimeout;
-			Connection.Session.SetTimeout(commandTimeout == 0 ? Constants.InfiniteTimeout : commandTimeout * 1000);
+			Connection?.Session?.SetTimeout(commandTimeout == 0 ? Constants.InfiniteTimeout : commandTimeout * 1000);
 		}
 
 		private void VerifyNotDisposed()

tests/SideBySide/CommandTests.cs

@@ -0,0 +1,44 @@
+using System;
+using MySql.Data.MySqlClient;
+using Xunit;
+
+namespace SideBySide
+{
+	public class CommandTests : IClassFixture<DatabaseFixture>
+	{
+		public CommandTests(DatabaseFixture database)
+		{
+			m_database = database;
+		}
+
+		[Fact]
+		public void CreateCommandSetsConnection()
+		{
+			using (var command = m_database.Connection.CreateCommand())
+			{
+				Assert.Equal(m_database.Connection, command.Connection);
+			}
+		}
+
+		[Fact]
+		public void ExecuteReaderRequiresConnection()
+		{
+			using (var command = new MySqlCommand())
+			{
+				Assert.Throws<InvalidOperationException>(() => command.ExecuteReader());
+			}
+		}
+
+		[Fact]
+		public void ExecuteReaderRequiresOpenConnection()
+		{
+			using (var connection = new MySqlConnection())
+			using (var command = connection.CreateCommand())
+			{
+				Assert.Throws<InvalidOperationException>(() => command.ExecuteReader());
+			}
+		}
+
+		readonly DatabaseFixture m_database;
+	}
+}