Splitbar can get stuck

[ChristophMueller87]

We are using the ui-splitbar in our application and have 3 contains in a row, all of them have a minimum size. When resizing the window to be very small and moving the sliders afterwards they can get stuck even when maximizing the window again.

This seems to be connected to the fact that the uncollapsed size of containers is saved and preserved even when resizing the window.

This happened with the 1.4.2 release.