fix: issue 226

Checking if the TaskUpdate has an update message before trying to
convert it.

Signed-off-by: Emmanuel Hugonnet <[email protected]>

Author: ehsavoie

spec-grpc/src/main/java/io/a2a/grpc/utils/ProtoUtils.java

@@ -824,7 +824,7 @@ private static DataPart dataPart(io.a2a.grpc.DataPart dataPart) {
         private static TaskStatus taskStatus(io.a2a.grpc.TaskStatus taskStatus) {
             return new TaskStatus(
                     taskState(taskStatus.getState()),
-                    message(taskStatus.getUpdate()),
+                    taskStatus.hasUpdate() ? message(taskStatus.getUpdate()) : null,
                     LocalDateTime.ofInstant(Instant.ofEpochSecond(taskStatus.getTimestamp().getSeconds(), taskStatus.getTimestamp().getNanos()), ZoneOffset.UTC)
             );
         }