Workaround hangs happening with default layout at some resolutions (1366 x 768 for example)

For some screen resolution the default settings produce window layout, where info panel is too small.
When info panel is too small, it produces a weird hangs.

How to reproduce:
* Add following dock configuration into your settings:
dock.dialog.1.contents=navigator - info pal_edit - tool_options history canvases - layers groups
dock.dialog.1.contents_size=122 92 168
* Start synfig
* Create circle
* Move navigator panel into the different dock place
* Try to do something after that - Synfig will hang.

(For some reason it happens for navigator only, but it is related with the size of info panel).

In the future we should set restrictions for the info panel size.