Prevent ANE when resource state is null (#1977)

Ideally we'd make the field nullable on the proto definition, but that's a breaking change at this point. So instead, we pass an empty string.

Other options are discussed in #1930.

Co-authored-by: Drew Noakes <git@drewnoakes.com>

src/Aspire.Hosting/Dashboard/proto/Partials.cs

@@ -16,7 +16,7 @@ public static Resource FromSnapshot(ResourceSnapshot snapshot)
             ResourceType = snapshot.ResourceType,
             DisplayName = snapshot.DisplayName,
             Uid = snapshot.Uid,
-            State = snapshot.State,
+            State = snapshot.State ?? "",
         };
 
         if (snapshot.CreationTimeStamp.HasValue)