[FEM] fix possible crash on changing the VectorMode

- if pvtu file filtering is on, there is by design not on every call of WriteColorData() data
  (on other occasions of GetArray(array) the result is checked, for two calls is was forgotten)

- also some automatic code formatting according to our current clang file

src/Mod/Fem/Gui/ViewProviderFemPostObject.cpp

@@ -362,8 +362,9 @@ void ViewProviderFemPostObject::updateProperties() {
         colorArrays.emplace_back("Not a vector");
     else {
         int array = Field.getValue() - 1; //0 is none
-        vtkPolyData* pd = m_currentAlgorithm->GetOutput();
-        vtkDataArray* data = pd->GetPointData()->GetArray(array);
+        vtkDataArray* data = point->GetArray(array);
+        if (!data)
+            return;
 
         if (data->GetNumberOfComponents() == 1)
             colorArrays.emplace_back("Not a vector");
@@ -494,7 +495,6 @@ void ViewProviderFemPostObject::update3D() {
 void ViewProviderFemPostObject::WritePointData(vtkPoints* points, vtkDataArray* normals,
                                                vtkDataArray* tcoords)
 {
-
     Q_UNUSED(tcoords);
 
     if (!points)
@@ -542,8 +542,8 @@ void ViewProviderFemPostObject::updateMaterial()
     WriteColorData(true);
 }
 
-void ViewProviderFemPostObject::WriteColorData(bool ResetColorBarRange) {
-
+void ViewProviderFemPostObject::WriteColorData(bool ResetColorBarRange)
+{
     if (!setupPipeline())
         return;
 
@@ -562,6 +562,8 @@ void ViewProviderFemPostObject::WriteColorData(bool ResetColorBarRange) {
     int array = Field.getValue() - 1; // 0 is none
     vtkPolyData* pd = m_currentAlgorithm->GetOutput();
     vtkDataArray* data = pd->GetPointData()->GetArray(array);
+    if (!data)
+        return;
 
     int component = VectorMode.getValue() - 1; // 0 is either "Not a vector" or magnitude,
                                                // for -1 is correct for magnitude.
@@ -610,8 +612,8 @@ void ViewProviderFemPostObject::WriteColorData(bool ResetColorBarRange) {
     m_triangleStrips->touch();
 }
 
-void ViewProviderFemPostObject::WriteTransparency() {
-
+void ViewProviderFemPostObject::WriteTransparency()
+{
     float trans = float(Transparency.getValue()) / 100.0;
     m_material->transparency.setValue(trans);
 
@@ -620,8 +622,8 @@ void ViewProviderFemPostObject::WriteTransparency() {
     m_triangleStrips->touch();
 }
 
-void ViewProviderFemPostObject::updateData(const App::Property* p) {
-
+void ViewProviderFemPostObject::updateData(const App::Property* p)
+{
     if (strcmp(p->getName(), "Data") == 0) {
         updateVtk();
     }
@@ -653,6 +655,7 @@ void ViewProviderFemPostObject::filterArtifacts(vtkDataObject* data)
     Gui::Document* doc = this->getDocument();
     Gui::View3DInventor* view =
         qobject_cast<Gui::View3DInventor*>(doc->getViewOfViewProvider(this));
+
     if (view) {
         Gui::View3DInventorViewer* viewer = view->getViewer();
         SbBox3f boundingBox;
@@ -683,7 +686,7 @@ void ViewProviderFemPostObject::filterArtifacts(vtkDataObject* data)
     this->Visibility.setValue(visibility);
 }
 
-    bool ViewProviderFemPostObject::setupPipeline()
+bool ViewProviderFemPostObject::setupPipeline()
 {
     vtkDataObject* data = static_cast<Fem::FemPostObject*>(getObject())->Data.getValue();
     if (!data)
@@ -718,8 +721,8 @@ void ViewProviderFemPostObject::filterArtifacts(vtkDataObject* data)
     return true;
 }
 
-void ViewProviderFemPostObject::onChanged(const App::Property* prop) {
-
+void ViewProviderFemPostObject::onChanged(const App::Property* prop)
+{
     if (m_blockPropertyChanges)
         return;
 
@@ -748,7 +751,8 @@ void ViewProviderFemPostObject::onChanged(const App::Property* prop) {
     ViewProviderDocumentObject::onChanged(prop);
 }
 
-bool ViewProviderFemPostObject::doubleClicked() {
+bool ViewProviderFemPostObject::doubleClicked()
+{
     // work around for a problem in VTK implementation:
     // https://forum.freecadweb.org/viewtopic.php?t=10587&start=130#p125688
     // check if backlight is enabled
@@ -764,8 +768,8 @@ bool ViewProviderFemPostObject::doubleClicked() {
     return true;
 }
 
-bool ViewProviderFemPostObject::setEdit(int ModNum) {
-
+bool ViewProviderFemPostObject::setEdit(int ModNum)
+{
     if (ModNum == ViewProvider::Default || ModNum == 1) {
 
         Gui::TaskView::TaskDialog* dlg = Gui::Control().activeDialog();
@@ -802,8 +806,8 @@ bool ViewProviderFemPostObject::setEdit(int ModNum) {
     }
 }
 
-void ViewProviderFemPostObject::setupTaskDialog(TaskDlgPost* dlg) {
-
+void ViewProviderFemPostObject::setupTaskDialog(TaskDlgPost* dlg)
+{
     dlg->appendBox(new TaskPostDisplay(this));
 }
 
@@ -821,7 +825,8 @@ void ViewProviderFemPostObject::unsetEdit(int ModNum) {
     }
 }
 
-void ViewProviderFemPostObject::hide() {
+void ViewProviderFemPostObject::hide()
+{
     Gui::ViewProviderDocumentObject::hide();
     m_colorStyle->style = SoDrawStyle::INVISIBLE;
     // The object is now hidden but the color bar is wrong
@@ -856,7 +861,8 @@ void ViewProviderFemPostObject::hide() {
     }
 }
 
-void ViewProviderFemPostObject::show() {
+void ViewProviderFemPostObject::show()
+{
     Gui::ViewProviderDocumentObject::show();
     m_colorStyle->style = SoDrawStyle::FILLED;
     // we must update the color bar except for data point filters
@@ -864,7 +870,8 @@ void ViewProviderFemPostObject::show() {
     WriteColorData(true);
 }
 
-void ViewProviderFemPostObject::OnChange(Base::Subject< int >& /*rCaller*/, int /*rcReason*/) {
+void ViewProviderFemPostObject::OnChange(Base::Subject< int >& /*rCaller*/, int /*rcReason*/)
+{
     bool ResetColorBarRange = false;
     WriteColorData(ResetColorBarRange);
 }