test: fix coverity warning in test

Fix uninitialized pointer field warning in test

Signed-off-by: Michael Dawson <mdawson@devrus.com>

PR-URL: #43631
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/cctest/test_inspector_socket_server.cc

@@ -301,11 +301,11 @@ class ServerHolder {
 
 class TestSocketServerDelegate : public SocketServerDelegate {
  public:
-  explicit TestSocketServerDelegate(
-      ServerHolder* server,
-      const std::vector<std::string>& target_ids)
+  explicit TestSocketServerDelegate(ServerHolder* server,
+                                    const std::vector<std::string>& target_ids)
       : harness_(server),
         targets_(target_ids),
+        server_(nullptr),
         session_id_(0) {}
 
   ~TestSocketServerDelegate() override {