fix: compile error on esp32 github actions (#58)

good fix. thank you

Author: hideakitai

src/EthernetClient.cpp

@@ -534,9 +534,9 @@ UIPClient::_allocateData()
       uip_userdata_t* data = &UIPClient::all_data[sock];
       if (!data->state)
         {
-          memset(data, 0, sizeof(uip_userdata_t));
-          data->conn_index = uip_conn - uip_conns; // pointer arithmetics
-          data->state = UIP_CLIENT_CONNECTED;
+          *data = uip_userdata_t();
+          data->conn_index = uip_conn - uip_conns; // pointer arithmetics
+          data->state = UIP_CLIENT_CONNECTED;
           return data;
         }
     }

src/EthernetUdp.cpp

@@ -34,9 +34,9 @@ extern "C" {
 
 // Constructor
 UIPUDP::UIPUDP() :
-    _uip_udp_conn(NULL)
+    _uip_udp_conn(NULL),
+    appdata()
 {
-  memset(&appdata,0,sizeof(appdata));
 }
 
 // initialize, start listening on specified port. Returns 1 if successful, 0 if there are no sockets available to use
@@ -68,7 +68,7 @@ UIPUDP::stop()
       Enc28J60Network::freeBlock(appdata.packet_in);
       _flushBlocks(appdata.packet_next);
       Enc28J60Network::freeBlock(appdata.packet_out);
-      memset(&appdata,0,sizeof(appdata));
+      appdata = uip_udp_userdata_t();
     }
 }