This fix is similar to the previous commit but more speculative, as we
currently don't have a bug scenario for it. Still, it seems to be wrong to
call PrepareForItem() just before GetLineStart() which undoes its effect, so
exchange the order of the calls.
See #16132.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76213 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775