xfer plugin buffer does not "refresh" properly

[mario-campos]

When doing a transfer with the xfer plugin, WeeChat will keep a progress bar in the xfer buffer and refresh it periodically to update the progress bar. In the terminal, this works well.

However, in Glowing Bear, the buffer output is displayed immediately, and then it disappears, not to show again. Unless you close the xfer buffer and reopen it. Then it does it again: displays the progress bar momentarily before it disappears again.