Fix out of bounds table offset panic

[benhall-7]

So I have a TUI project I'm working on where I've supplied a method to filter out data from the Table widget, using a regex match. Whenever I do this I want to preserve the previous table state, so that the table can still scroll up or down relative to its previous position. For example, if just 1 entry were removed it would be preferable to preserve the offset instead of reset it to 0 and scroll down to the currently selected element. The issue this led to was an out-of-bounds index whenever the offset was greater than the length of the new data. The fix takes only 1 line: clamp the offset to the last index in the new list.

[fdehau]

Thanks a lot for the detailed report. I've fixed this in #516 to add tests and fix it in List which had the same issue.