Merge pull request #537 from tomekpanek:listSessions-returns-sessions-with-empty-state

PiperOrigin-RevId: 825402273

Author: copybara-github

core/src/main/java/com/google/adk/sessions/VertexAiSessionService.java

@@ -138,7 +138,12 @@ private ListSessionsResponse parseListSessionsResponse(
           Session.builder(sessionId)
               .appName(appName)
               .userId(userId)
-              .state(new ConcurrentHashMap<>())
+              .state(
+                  apiSession.get("sessionState") == null
+                      ? new ConcurrentHashMap<>()
+                      : objectMapper.convertValue(
+                          apiSession.get("sessionState"),
+                          new TypeReference<ConcurrentMap<String, Object>>() {}))
               .lastUpdateTime(updateTimestamp)
               .build();
       sessions.add(session);