Fixed crash of build under OSX and Linux.

+ Added flag to control if application rescale is possible

src/slic3r/GUI/MainFrame.hpp

@@ -44,6 +44,8 @@ struct PresetTab {
 class MainFrame : public DPIFrame
 {
     bool        m_loaded {false};
+    bool        m_can_rescale_application {true};
+    float       m_scale_factor_cache;
 
     wxString    m_qs_last_input_file = wxEmptyString;
     wxString    m_qs_last_output_file = wxEmptyString;