PartDesign: Unify deletion behavior

This unifies deletion behavior for all PartDesign features ensuring that
sketches that were used to create these features show after deletion and
that the tip is properly transfered.

src/Mod/PartDesign/Gui/ViewProvider.cpp

@@ -249,6 +249,15 @@ void ViewProvider::updatePreview()
     }
 }
 
+void ViewProvider::makeChildrenVisible()
+{
+    for (const auto child : claimChildren()) {
+        if (auto vp = Gui::Application::Instance->getViewProvider(child)) {
+            vp->show();
+        }
+    }
+}
+
 void ViewProvider::onChanged(const App::Property* prop) {
 
     //if the object is inside of a body we make sure it is the only visible one on activation
@@ -340,6 +349,8 @@ bool ViewProvider::onDelete(const std::vector<std::string>&)
         FCMD_OBJ_CMD(body, "removeObject(" << Gui::Command::getObjectCmd(feature) << ')');
     }
 
+    makeChildrenVisible();
+
     return true;
 }