Fix possible NRE (netcoreapp3.1 only?)

Author: commonsensesoftware

src/AspNetCore/OData/src/Asp.Versioning.OData.ApiExplorer/ApiExplorer/ODataApiDescriptionProvider.cs

@@ -102,7 +102,13 @@ public virtual void OnProvidersExecuted( ApiDescriptionProviderContext context )
         for ( var i = results.Count - 1; i >= 0; i-- )
         {
             var result = results[i];
-            var metadata = result.ActionDescriptor.EndpointMetadata.OfType<IODataRoutingMetadata>().ToArray();
+
+            if ( result.ActionDescriptor.EndpointMetadata is not IList<object> endpointMetadata )
+            {
+                continue;
+            }
+
+            var metadata = endpointMetadata.OfType<IODataRoutingMetadata>().ToArray();
             var notOData = metadata.Length == 0;
 
             if ( notOData )

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc.ApiExplorer/VersionedApiDescriptionProvider.cs

@@ -179,6 +179,11 @@ private static bool IsUnversioned( ActionDescriptor action )
     {
         var endpointMetadata = action.EndpointMetadata;
 
+        if ( endpointMetadata == null )
+        {
+            return true;
+        }
+
         for ( var i = 0; i < endpointMetadata.Count; i++ )
         {
             if ( endpointMetadata[i] is ApiVersionMetadata )

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc/Abstractions/ActionDescriptorExtensions.cs

@@ -24,6 +24,11 @@ public static ApiVersionMetadata GetApiVersionMetadata( this ActionDescriptor ac
 
         var endpointMetadata = action.EndpointMetadata;
 
+        if ( endpointMetadata == null )
+        {
+            return ApiVersionMetadata.Empty;
+        }
+
         for ( var i = 0; i < endpointMetadata.Count; i++ )
         {
             if ( endpointMetadata[i] is ApiVersionMetadata metadata )
@@ -39,6 +44,12 @@ internal static void AddOrReplaceApiVersionMetadata( this ActionDescriptor actio
     {
         var endpointMetadata = action.EndpointMetadata;
 
+        if ( endpointMetadata == null )
+        {
+            action.EndpointMetadata = new List<object>() { value };
+            return;
+        }
+
         for ( var i = 0; i < endpointMetadata.Count; i++ )
         {
             if ( endpointMetadata[i] is not ApiVersionMetadata )