[plugin_installer] 'NoneType' object has no attribute 'get_selected'

Versions

• OS: Ubuntu 19.04
• GTK+ Version: 3.24.8
• PyGObject Version: 3.32.0
• python-nbxmpp Version: 0.6.10
• Gajim Version: 1.1.3+gajim@b63dd2ed

Traceback

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/gajim/./data/plugins/plugin_installer/plugin_installer.py", line 350, in select_root_iter
    model, iter_ = selection.get_selected()
AttributeError: 'NoneType' object has no attribute 'get_selected'

Steps to reproduce the problem

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