Don't assert if an already hidden/shown row/column is being hidden/shown again but simply don't do anything. This is more convenient because the code outside wxGrid has no efficient way to only hide a row/column if it's currently shown. Closes #14960. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73366 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775