Remove the useless condition check (#1021)

Co-authored-by: Yichen Wang <18348405+Aiee@users.noreply.github.com>
Co-authored-by: Yee <2520865+yixinglu@users.noreply.github.com>

src/service/SessionManager.cpp

@@ -72,9 +72,7 @@ std::shared_ptr<Session> SessionManager::removeSession(int64_t id) {
 
 int64_t SessionManager::newSessionId() {
     int64_t id = ++nextId_;
-    if (id == 0) {
-        id = ++nextId_;
-    }
+    DCHECK_GT(id, 0);
     return id;
 }