fix: warnings

UnitTest/StunClien5389UDPTest.cs

@@ -84,7 +84,7 @@ public class StunClien5389UDPTest
 	public async Task MappingBehaviorTestUnsupportedServerAsync()
 	{
 		Mock<StunClient5389UDP> mock = new(ServerAddress, Any, default!);
-		StunClient5389UDP? client = mock.Object;
+		StunClient5389UDP client = mock.Object;
 
 		StunResult5389 r1 = new()
 		{
@@ -351,7 +351,7 @@ public class StunClien5389UDPTest
 	public async Task FilteringBehaviorTestUnsupportedServerAsync()
 	{
 		Mock<StunClient5389UDP> mock = new(ServerAddress, Any, default!);
-		StunClient5389UDP? client = mock.Object;
+		StunClient5389UDP client = mock.Object;
 
 		StunResult5389 r1 = new()
 		{

UnitTest/StunClient3489Test.cs

@@ -47,7 +47,7 @@ public class StunClient3489Test
 	public async Task UnsupportedServerTestAsync()
 	{
 		Mock<StunClient3489> mock = new(Any, Any, default!);
-		StunClient3489? client = mock.Object;
+		StunClient3489 client = mock.Object;
 
 		mock.Setup(x => x.LocalEndPoint).Returns(LocalAddress1);
 		StunResponse unknownResponse = new(DefaultStunMessage, Any, LocalAddress1);
@@ -151,7 +151,7 @@ public class StunClient3489Test
 	public async Task FullConeTestAsync()
 	{
 		Mock<StunClient3489> mock = new(Any, Any, default!);
-		StunClient3489? client = mock.Object;
+		StunClient3489 client = mock.Object;
 
 		StunResponse test1Response = new(
 			new StunMessage5389