[PD] remove superfluous nullptr checks

src/Mod/PartDesign/Gui/TaskHelixParameters.cpp

@@ -460,7 +460,7 @@ void TaskHelixParameters::onAxisChanged(int num)
         oldRefName = oldSubRefAxis.front();
 
     App::PropertyLinkSub& lnk = *(axesInList[num]);
-    if (lnk.getValue() == nullptr) {
+    if (!lnk.getValue()) {
         // enter reference selection mode
         TaskSketchBasedParameters::onSelectReference(
             AllowSelection::EDGE |
@@ -587,7 +587,7 @@ void TaskHelixParameters::getReferenceAxis(App::DocumentObject*& obj, std::vecto
 
     int num = ui->axis->currentIndex();
     const App::PropertyLinkSub& lnk = *(axesInList.at(num));
-    if (lnk.getValue() == nullptr) {
+    if (!lnk.getValue()) {
         throw Base::RuntimeError("Still in reference selection mode; reference wasn't selected yet");
     }
     else {