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/dialogs/dialogs.cpp

@@ -238,6 +238,9 @@ MyCanvas *myCanvas = (MyCanvas *) NULL;
 // `Main program' equivalent, creating windows and returning main app frame
 bool MyApp::OnInit()
 {
+    if ( !wxApp::OnInit() )
+        return false;
+
 #if wxUSE_IMAGE
     wxInitAllImageHandlers();
 #endif