fix potential NPE

.gitignore

@@ -278,3 +278,9 @@ BUCKAROO_DEPS
 # Vim
 *.swp
 *.swo
+
+# clangd
+.cache/
+
+# Claude Code
+.claude/settings.local.json

timeplus/client_pool.cpp

@@ -30,15 +30,17 @@ ClientPool::ClientPtr ClientPool::Acquire(int64_t timeout_ms) {
 }
 
 void ClientPool::GuardedClient::TestConnection() noexcept {
+    if (!client) {
+        valid = false;
+        return;
+    }
+
     try {
         client->Ping();
         valid = true;
     } catch (...) {
         valid = false;
     }
-
-    TRACE("test connection: host=%s port=%d valid=%s", client->GetCurrentEndpoint()->host.c_str(), client->GetCurrentEndpoint()->port,
-          valid ? "true" : "false");
 }
 
 }  // namespace timeplus

timeplus/client_pool.h

@@ -47,7 +47,7 @@ class ClientPool {
 
         GuardedClient& operator=(GuardedClient&& other) noexcept {
             if (this != &other) {
-                if (pool_ && client) {
+                if (pool_) {
                     pool_->Release(std::move(client), valid);
                 }
                 pool_ = other.pool_;

ut/client_pool_ut.cpp

@@ -44,3 +44,18 @@ TEST(ClientPool, BadHost) {
 
     ASSERT_THROW(pool.Acquire(1000), std::system_error);
 }
+
+TEST(ClientPool, GuardedClientResetStillReturnsSlot) {
+    ClientOptions client_options;
+    client_options.host = "localhost";
+    ClientPool pool{client_options, /*pool_size=*/1};
+
+    {
+        auto guarded = pool.GetGuardedClient(1000);
+        ASSERT_NE(guarded.client, nullptr);
+        guarded.client.reset();
+    }
+
+    auto client = pool.Acquire(100);
+    ASSERT_NE(client, nullptr);
+}