fix null pointer error

com.unity.perception/Runtime/GroundTruth/SimulationState.cs

                 }
             }
 
-            var values2 = new List<object>();
-            foreach (var v in values)
+            List<object> values2 = null;
+            if (values != null)
-                values2.Add(v);
+                values2 = new List<object>();
+                foreach (var v in values)
+                {
+                    values2.Add(v);
+                }
+
             ReportAsyncAnnotationResult(asyncAnnotation, filename, jArray, values:values2);
         }