[FEM] fix plots of line filter

- when the line geometry changed, the axis data must be refreshed to get correct plots

src/Mod/Fem/App/FemPostFilter.h

@@ -117,11 +117,11 @@ public:
         return "FemGui::ViewProviderFemPostDataAlongLine";
     }
     virtual short int mustExecute(void) const;
+    void GetAxisData();
 
 protected:
     virtual App::DocumentObjectExecReturn* execute(void);
     virtual void onChanged(const App::Property* prop);
-    void GetAxisData();
     virtual void handleChangedPropertyType(Base::XMLReader& reader, const char* TypeName, App::Property* prop);
 
 private:

src/Mod/Fem/Gui/TaskPostBoxes.cpp

@@ -707,6 +707,8 @@ void TaskPostDataAlongLine::point1Changed(double) {
     // refresh the color bar range
     auto currentField = getTypedView<ViewProviderFemPostObject>()->Field.getValue();
     getTypedView<ViewProviderFemPostObject>()->Field.setValue(currentField);
+    // also the axis data must be refreshed to get correct plots
+    static_cast<Fem::FemPostDataAlongLineFilter*>(getObject())->GetAxisData();
 }
 
 void TaskPostDataAlongLine::point2Changed(double) {
@@ -720,6 +722,8 @@ void TaskPostDataAlongLine::point2Changed(double) {
     // refresh the color bar range
     auto currentField = getTypedView<ViewProviderFemPostObject>()->Field.getValue();
     getTypedView<ViewProviderFemPostObject>()->Field.setValue(currentField);
+    // also the axis data must be refreshed to get correct plots
+    static_cast<Fem::FemPostDataAlongLineFilter*>(getObject())->GetAxisData();
 }
 
 void TaskPostDataAlongLine::resolutionChanged(int val) {