Bugfix for #3530. (Instead of r30557)
(The problem was:
1. click into the last row,
2. click on "use as text" button,
3. edit the text,
4. press enter
Most of cases the text in the cell won't be the updated text, but it will the same as was before the 3. point.)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@30658 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e