Layers dialog: typeahead find takes to (root) layer

Partly migrated from: https://bugs.launchpad.net/inkscape/+bug/505225, see also #804 (moved)

Steps to reproduce:

• open Inkscape
• open the layers dialog
• click the "eye" icon next to a layer
• type a shortcut (e.g. "b" to go to the bezier curve tool)

What happened?

• A text input bar is visible
• when the text input bar fades, the "layer" combobox at the bottom shows (root) (you start working directly in the root layer, not a regular layer)

What should have happened?

Inkscape switches to the Bezier curve tool

Inkscape Version and Operating System:

• Inkscape Version: 1.1-dev (3322b9c, 2019-12-31)
• Operating System: Windows 10
• Operating System version: 10.0.18362

Additionals from the original Launchpad bug:

• Related: #376 (moved)