NEO-61: fix null snapshot on depletion deny path.

Check TryGetRemainingGathers return before using the out snapshot;
default struct had null InteractableId and threw on .Length.

server/NeonSprawl.Server/Game/Gathering/ResourceNodeInstanceOperations.cs

@@ -38,10 +38,14 @@ public static class ResourceNodeInstanceOperations
                 new ResourceNodeInstanceSnapshot(key, remaining));
         }
 
-        store.TryGetRemainingGathers(key, out var current);
+        if (!store.TryGetRemainingGathers(key, out var current))
+        {
+            current = new ResourceNodeInstanceSnapshot(key, 0);
+        }
+
         return new ResourceNodeInstanceMutationOutcome(
             ResourceNodeInstanceMutationKind.Denied,
             ResourceNodeInstanceReasonCodes.NodeDepleted,
-            current.InteractableId.Length > 0 ? current : new ResourceNodeInstanceSnapshot(key, 0));
+            current);
     }
 }