textctrl.cpp: Removed assert from CanRedo/CanUndo since the best behaviour is

to return FALSE (Redo/Undo functions are unimplemented)
treectrlg.cpp: in InsertItem, allow previous item to be null in order
to insert at first position of possibly-empty child list
dcclient.cpp: allow setting of null font (common espec. on Windows)


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@15540 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk1/dcclient.cpp

@@ -1594,7 +1594,9 @@ void wxWindowDC::Clear()
 
 void wxWindowDC::SetFont( const wxFont &font )
 {
-    wxCHECK_RET( font.Ok(), _T("invalid font in wxWindowDC::SetFont") );
+    // It is common practice to set the font to wxNullFont, so
+    // don't consider it to be an error
+    //    wxCHECK_RET( font.Ok(), _T("invalid font in wxWindowDC::SetFont") );
 
     m_font = font;
 #ifdef __WXGTK20__