Fixed broken custom pattern suggestion

Author: Bart Koelman

src/JsonApiDotNetCore/CollectionExtensions.cs

@@ -0,0 +1,21 @@
+using System.Collections.Generic;
+using System.Linq;
+using JetBrains.Annotations;
+
+namespace JsonApiDotNetCore
+{
+    internal static class CollectionExtensions
+    {
+        [Pure]
+        [ContractAnnotation("source: null => true")]
+        public static bool IsNullOrEmpty<T>(this IEnumerable<T> source)
+        {
+            if (source == null)
+            {
+                return true;
+            }
+
+            return !source.Any();
+        }
+    }
+}

src/JsonApiDotNetCore/Queries/Internal/QueryableBuilding/SelectClauseBuilder.cs

@@ -167,7 +167,7 @@ private Expression CreateAssignmentRightHandSideForLayer(QueryLayer layer, Lambd
                 return CreateCollectionInitializer(outerLambdaScope, selectorPropertyInfo, bodyElementType, layer, lambdaScopeFactory);
             }
 
-            if (layer.Projection == null || !layer.Projection.Any())
+            if (layer.Projection.IsNullOrEmpty())
             {
                 return propertyAccess;
             }

src/JsonApiDotNetCore/Serialization/RequestDeserializer.cs

@@ -68,7 +68,7 @@ private object DeserializeOperationsDocument(string body)
             JToken bodyToken = LoadJToken(body);
             var document = bodyToken.ToObject<AtomicOperationsDocument>();
 
-            if (document?.Operations == null || !document.Operations.Any())
+            if ((document?.Operations).IsNullOrEmpty())
             {
                 throw new JsonApiSerializationException("No operations found.", null);
             }