[FLINK-25936][java-sdk] Adjust the ConcurrentAddressScopedStorageTest to reflect the request-reply protocol

According to the request reply protocol, in case of a missing value: a registered state
but without an assosciated value (deleted, expired, or simply never set) the invocation
will contain an associated TypedValue with the field has_value = false, and might or might not
provide the type_name field.
This commit refelects that in the test.
diff --git a/statefun-sdk-java/src/test/java/org/apache/flink/statefun/sdk/java/storage/ConcurrentAddressScopedStorageTest.java b/statefun-sdk-java/src/test/java/org/apache/flink/statefun/sdk/java/storage/ConcurrentAddressScopedStorageTest.java
index cb075e2..03de72d 100644
--- a/statefun-sdk-java/src/test/java/org/apache/flink/statefun/sdk/java/storage/ConcurrentAddressScopedStorageTest.java
+++ b/statefun-sdk-java/src/test/java/org/apache/flink/statefun/sdk/java/storage/ConcurrentAddressScopedStorageTest.java
@@ -189,7 +189,7 @@
             .setStateName(spec.name())
             .setStateValue(
                 TypedValue.newBuilder()
-                    .setTypename(spec.type().typeName().asTypeNameString())
+                    .setTypename(value == null ? "" : spec.type().typeName().asTypeNameString())
                     .setHasValue(value != null)
                     .setValue(toByteString(spec.type(), value)))
             .build();