added wxDialog::GetParentForModalDialog() and use it to try to always create modal dialogs with a parent (slightly modified patch 1702962)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45588 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/filedlg.cpp

@@ -154,6 +154,8 @@ wxFileDialog::wxFileDialog(wxWindow *parent, const wxString& message,
 
     m_needParent = false;
 
+    parent = GetParentForModalDialog(parent);
+
     if (!PreCreation(parent, pos, wxDefaultSize) ||
         !CreateBase(parent, wxID_ANY, pos, wxDefaultSize, style,
                 wxDefaultValidator, wxT("filedialog")))