Fix implicit cast of null and BooleanOr

Author: bjorkstromm

src/Protocol/Models/BooleanOr.cs

@@ -48,7 +48,7 @@ public object RawValue
 
         public static implicit operator BooleanOr<T>(T value)
         {
-            return new BooleanOr<T>(value);
+            return value != null ? new BooleanOr<T>(value) : null;
         }
 
         public static implicit operator BooleanOr<T>(bool value)

test/Lsp.Tests/Capabilities/Server/ServerCapabilitiesTests.cs

@@ -5,6 +5,7 @@
 using Newtonsoft.Json.Linq;
 using OmniSharp.Extensions.LanguageServer.Protocol;
 using OmniSharp.Extensions.LanguageServer.Protocol.Client.Capabilities;
+using OmniSharp.Extensions.LanguageServer.Protocol.Models;
 using OmniSharp.Extensions.LanguageServer.Protocol.Serialization;
 using OmniSharp.Extensions.LanguageServer.Protocol.Server.Capabilities;
 using Xunit;
@@ -75,7 +76,9 @@ public void SimpleTest(string expected)
         [Theory, JsonFixture]
         public void Optional(string expected)
         {
-            var model = new ServerCapabilities();
+            var model = new ServerCapabilities {
+                ColorProvider = (ColorOptions)null
+            };
 
             var result = Fixture.SerializeObject(model);