Filter out blank lines

Response from the provider has changed so that there are blank lines at the end, which leads to the result can not be parsed correctly

dnsapi/dns_ddnss.sh

@@ -119,7 +119,7 @@ _ddnss_rest() {
 
   # DDNSS uses GET to update domain info
   if [ "$method" = "GET" ]; then
-    response="$(_get "$url" | sed 's/<[a-zA-Z\/][^>]*>//g' | _tail_n 1)"
+    response="$(_get "$url" | sed 's/<[a-zA-Z\/][^>]*>//g' | tr -s "\n" | _tail_n 1)"
   else
     _err "Unsupported method"
     return 1