Widget sizing on startup

[dihm]

I've noticed this for a while now but haven't really bothered to look in to what was happening until now. For whatever reason, on first start, blacs doesn't resize widgets within tabs correctly. Getting correct sizing requires manually changing to container sizes.

I've done a little investigation but not made very much progress. Manually triggering various widget updates after everything is loaded doesn't help. Best guess at the moment is that the custom ToolPalette._layout_widgets() function is not getting the correct size on initial start.