[FIX] mail: Limit emojis quantity

If the user put more than 200 emojis, we didn't replace emoji with
image. But due to a typo in the code, this mechanism broke the
discuss application.

closes odoo/odoo#40734

X-original-commit: 0877cb6c84c768bd9fad46fa6f959635bb2353a5
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/js/models/messages/message.js

@@ -604,7 +604,7 @@ var Message =  AbstractMessage.extend(Mixins.EventDispatcherMixin, ServicesMixin
         _.each(emojis, function (emoji) {
             var unicode = emoji.unicode;
             var regexp = new RegExp("(?:^|\\s|<[a-z]*>)(" + unicode + ")(?=\\s|$|</[a-z]*>)", 'g');
-            var originalBody = self.body;
+            var originalBody = self._body;
             self._body = self._body.replace(regexp,
                 ' <span class="o_mail_emoji">' + unicode + '</span> ');
             // Idiot-proof limit. If the user had the amazing idea of