clickable nicknames fails in MUCs

Traceback (most recent call last):
  File "/home/bebe/.local/share/gajim/plugins/clickable_nicknames/clickable_nicknames.py", line 94, in on_textview_motion_notify_event
    tags = self.textview.tv.get_iter_at_location(x, y).get_tags()
AttributeError: '_ResultTuple' object has no attribute 'get_tags'

This happens in MUCs, when hovering the window. Sometimes it also occurs when hovering specific textbits. But it does not happen in private Chats at all.

Versions

• Plugins: current master (d3ee6070)
• Python: 3.6.4
• Distro: ArchLinux
• Gajim: Current master