Catch exception when trying to share (#1203)

* Fix crash

* Fix errors

src/Calculator/Views/GraphingCalculator/GraphingCalculator.xaml.h

@@ -106,6 +106,7 @@ public ref class GraphingCalculator sealed : public Windows::UI::Xaml::Data::INo
         void OnVisualStateChanged(Platform::Object ^ sender, Windows::UI::Xaml::VisualStateChangedEventArgs ^ e);
         std::wstringstream FormatTraceValue(double min, double max, float pointValue);
         void GraphViewButton_Click(Platform::Object ^ sender, Windows::UI::Xaml::RoutedEventArgs ^ e);
+        void ShowShareError();
     };
 
 }