Fix nullable warnings in FlagsmithClient

Co-authored-by: Claude <noreply@anthropic.com>

Author: emyller

Flagsmith.FlagsmithClient/FlagsmithClient.cs

@@ -177,7 +177,7 @@ public async Task<IFlags> GetIdentityFlagsFromCorrectSource(IdentityWrapper iden
 
             var segments = result.Segments
                 .Where(s => s.Metadata.Id != null) // Not a real segment, e.g. an identity override virtual segment
-                .Select(s => new Segment(id: s.Metadata.Id.Value, name: s.Name))
+                .Select(s => new Segment(id: s.Metadata.Id!.Value, name: s.Name))
                 .ToList<ISegment>();
 
             return segments;

Flagsmith.FlagsmithClient/Metadata.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 namespace Flagsmith
 {
     /// <summary>