Fix "expand post" not restoring enough space in some cases.
Fix "expand post" not restoring enough space in some cases.

In same cases, the saved oldHeight could have become inaccurate due
to, for example, loaded images. This commit fixes this issue by
reverting the property to its default value of "auto" instead.

TechnoDann/PPC-board-2.0,TechnoDann/PPC-board-2.0,TechnoDann/PPC-board-2.0,TechnoDann/PPC-board-2.0