[UI] button's label: [objet Object]

Pydio 2.0.3
From https://github.com/pydio/cells/issues/213

When hovering a button [objet Object] is shown:

Example of the “master key” list:

Screenshot from 2020-03-03 14-50-06

Example of the “plugins” list:

Screenshot from 2020-03-03 14-50-59