call OnInit() from all samples to allow using standard command line options with all of them (patch 1623971)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@44354 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/printing/printing.cpp

@@ -77,6 +77,9 @@ bool WritePageHeader(wxPrintout *printout, wxDC *dc, const wxChar *text, float m
 
 bool MyApp::OnInit(void)
 {
+    if ( !wxApp::OnInit() )
+        return false;
+
     wxInitAllImageHandlers();
 
     m_testFont.Create(10, wxSWISS, wxNORMAL, wxNORMAL);