Sometimes inserting a table in a list item that already has a table nests the tables in IE8

This bug deals with the new tables in list feature added in #404.

In IE8, there are consistently two different `br` spacers that you can select after a table (two rows for your cursor). They cause weird things when there are multiple tables. If your cursor is in the space immediately following a table (not the second one), doing a table insertion does really weird nesting of the two tables. The correct behavior would be to insert the table after that table with a spacer `br` added between the two tables afterwards.

To reproduce:

1. Start by running this [unit test](http://192.168.1.72:8080/test/unit/index.html?filter=list-indent_outdent%3A%20First-level%20no-sublist%20previous-sublist&jquery=1.8.0)
2. Put your cursor right after the `8`.
3. Insert a table
4. Click to move your cursor to the second "row" of space, right below where it ends up.
5. Click to move your cursor back to the first "row" of space, right below the table.
6. Insert a table

The tables get nested together in a really strange way.