Merge branch 'master' into 'feature-3617-1'

# Conflicts:
#   dap-sdk/net/server/http_server/dap_http_simple.c

modules/net/dap_dns_server.c

@@ -322,6 +322,9 @@ void dap_dns_server_start() {
 }
 
 void dap_dns_server_stop() {
+    if(!s_dns_server)
+        return;
+
     dap_dns_zone_hash_t *current_zone, *tmp;
     HASH_ITER(hh, s_dns_server->hash_table, current_zone, tmp) {
         HASH_DEL(s_dns_server->hash_table, current_zone);

modules/service/xchange/dap_chain_net_srv_xchange.c

@@ -87,6 +87,8 @@ int dap_chain_net_srv_xchange_init()
 
 void dap_chain_net_srv_xchange_deinit()
 {
+    if(!s_srv_xchange)
+        return;
     dap_chain_net_srv_xchange_price_t *l_price = NULL, *l_tmp;
     HASH_ITER(hh, s_srv_xchange->pricelist, l_price, l_tmp) {
         HASH_DEL(s_srv_xchange->pricelist, l_price);