[wpinet] uv: Stop creating handles when closing loop (#5102)

This prevents EventLoopRunner::Stop() from hanging in the case when
new handles are created after the async walk closes all the handles.

wpinet/src/main/native/cpp/DsClient.cpp

@@ -21,6 +21,9 @@ DsClient::DsClient(wpi::uv::Loop& loop, wpi::Logger& logger,
     : m_logger{logger},
       m_tcp{uv::Tcp::Create(loop)},
       m_timer{uv::Timer::Create(loop)} {
+  if (!m_tcp || !m_timer) {
+    return;
+  }
   m_tcp->end.connect([this] {
     WPI_DEBUG4(m_logger, "DS connection closed");
     clearIp();