Fix CI (#563)

Author: kayoub5

Diff for: SharpPcap/SharpPcap.csproj

@@ -28,7 +28,7 @@ SPDX-License-Identifier: MIT
     <Deterministic>true</Deterministic>
     <Nullable>enable</Nullable>
     <WarningsAsErrors>Nullable</WarningsAsErrors>
-    <LangVersion>13.0</LangVersion>
+    <LangVersion>12.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(TargetFramework)' != 'netstandard2.0' ">
 	<IsTrimmable>true</IsTrimmable>

Diff for: Test/WinpkFilter/WinpkFilterDeviceTest.cs

@@ -70,7 +70,7 @@ public void Properties()
             {
                 Assert.That(device.Name, Is.Not.Null);
                 Assert.That(device.FriendlyName, Is.Not.Null);
-                Assert.That(device.Description, Is.Null);
+                Assert.That(device.Description, Is.Empty);
                 Assert.That(device.LastError, Is.Null);
                 Assert.That(device.Filter, Is.Null);
                 Assert.That(device.LinkType, Is.EqualTo(LinkLayers.Ethernet));