Fix #876: Verbatim() producing null match query

Author: gmarz

Diff for: src/Nest/Resolvers/Converters/Queries/MatchQueryJsonConverter.cs

@@ -73,7 +73,7 @@ public TReturn GetPropValue<TReturn>(JObject jObject, string propertyName)
 		public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
 		{
 			var v = value as IFieldNameQuery;
-			if (v == null || v.IsConditionless)
+			if (v == null)
 				return;
 
 			var fieldName = v.GetFieldName();

Diff for: src/Tests/Nest.Tests.Unit/Nest.Tests.Unit.csproj

@@ -369,6 +369,7 @@
     <Compile Include="Reproduce\Reproduce579Tests.cs" />
     <Compile Include="Reproduce\Reproduce860Tests.cs" />
     <Compile Include="Reproduce\Reproduce806Tests.cs" />
+    <Compile Include="Reproduce\Reproduce876Tests.cs" />
     <Compile Include="Search\Fields\FieldsTests.cs" />
     <Compile Include="Search\Filter\Modes\ConditionlessFilterJson.cs" />
     <Compile Include="Search\Filter\Modes\FilterModesTests.cs" />

Diff for: src/Tests/Nest.Tests.Unit/Reproduce/Issue876.json

@@ -0,0 +1,9 @@
+{
+  "query":  {
+    "match":  {
+      "name": {
+        "query": ""
+      }
+    }
+  }
+}

Diff for: src/Tests/Nest.Tests.Unit/Reproduce/Reproduce876Tests.cs

@@ -0,0 +1,31 @@
+using FluentAssertions;
+using Nest.Tests.MockData.Domain;
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Nest.Tests.Unit.Reproduce
+{
+	[TestFixture]
+	public class Reproduce876Tests : BaseJsonTests
+	{
+		[Test]
+		public void Issue876()
+		{
+			var result = new SearchDescriptor<ElasticsearchProject>()
+				.Query(q => q
+					.Verbatim()
+					.Match(m => m
+						.OnField(p => p.Name)
+						.Query(string.Empty)
+					)
+				);
+
+			this.JsonEquals(result, MethodInfo.GetCurrentMethod());
+		}
+	}
+}