irc: fix memory leak in IRC message parser

Bug was introduced in WeeChat 3.4 by commit
c4b4d80936.

ChangeLog.adoc

@@ -38,6 +38,7 @@ Bug fixes::
   * irc: fix display of country code in message 344 received as whois geo info (issue #1736)
   * irc: add missing "account-tag" in list of supported capabilities
   * irc: fix display of self CTCP message containing bold attribute (issue #1981)
+  * irc: fix memory leak in IRC message parser
   * script: fix cursor position after `/script list -i` or `/script list -il`
   * script: fix buffer used by command `/script list -i|-il|-o|-ol`
 

src/plugins/irc/irc-message.c

@@ -529,6 +529,8 @@ irc_message_parse_to_hashtable (struct t_irc_server *server,
         free (arguments);
     if (text)
         free (text);
+    if (params)
+        weechat_string_free_split (params);
 
     return hashtable;
 }