irc: return NULL in function irc_message_get_address_from_host if the received host is NULL

src/plugins/irc/irc-message.c

@@ -495,6 +495,9 @@ irc_message_get_address_from_host (const char *host)
     char host2[256], *pos_space, *pos;
     const char *ptr_host;
 
+    if (!host)
+        return NULL;
+
     address[0] = '\0';
     if (host)
     {

src/plugins/irc/irc-protocol.c

@@ -914,7 +914,7 @@ IRC_PROTOCOL_CALLBACK(chghost)
                     nick,
                     IRC_COLOR_CHAT_DELIMITERS,
                     IRC_COLOR_CHAT_HOST,
-                    address,
+                    (address) ? address : "",
                     IRC_COLOR_CHAT_DELIMITERS,
                     IRC_COLOR_MESSAGE_CHGHOST,
                     IRC_COLOR_CHAT_HOST,