Prevent seg fault for older GTK+

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@47023 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/filepicker.h

@@ -36,6 +36,7 @@
                                                                               \
     virtual bool Destroy()                                                    \
     {                                                                         \
+        if (m_dialog)                                                         \
             m_dialog->Destroy();                                              \
         return wxButton::Destroy();                                           \
     }                                                                         \

src/gtk/filepicker.cpp

@@ -105,6 +105,7 @@ wxFileButton::~wxFileButton()
     // GtkFileChooserDialog associated with m_dialog.
     // Thus we have to set its m_widget to NULL to avoid
     // double destruction on same widget
+    if (m_dialog)
         m_dialog->m_widget = NULL;
 }
 
@@ -126,6 +127,7 @@ void wxFileButton::OnDialogOK(wxCommandEvent& ev)
 void wxFileButton::SetPath(const wxString &str)
 {
     m_path = str;
+    if (m_dialog)
         UpdateDialogPath(m_dialog);
 }
 
@@ -249,6 +251,7 @@ wxDirButton::~wxDirButton()
     // GtkFileChooserDialog associated with m_dialog.
     // Thus we have to set its m_widget to NULL to avoid
     // double destruction on same widget
+    if (m_dialog)
         m_dialog->m_widget = NULL;
 }
 
@@ -263,6 +266,7 @@ void wxDirButton::SetPath(const wxString &str)
     // general with all wxWidgets control-manipulation functions which do not send events).
     m_bIgnoreNextChange = true;
 
+    if (m_dialog)
         UpdateDialogPath(m_dialog);
 }