TD: Fix loading project files

With PR 19941 there is a regression where parts of the document
won't be restored. This is caused by overriding the virtual method
handleChangedPropertyType() but not calling the method of the base class.

While searching for a fix another problem showed up where (due to the
incomplete loading) exceptions are thrown but not handled within TD.
Therefore the method recompute() is overridden in DrawView to also handle
OCC exceptions.

src/Mod/TechDraw/App/DrawView.cpp

@@ -110,6 +110,20 @@ DrawView::DrawView():
 }
 
 
+App::DocumentObjectExecReturn* DrawView::recompute()
+{
+    try {
+        return App::DocumentObject::recompute();
+    }
+    catch (Standard_Failure& e) {
+        auto ret = new App::DocumentObjectExecReturn(e.GetMessageString());
+        if (ret->Why.empty()) {
+            ret->Why = "Unknown OCC exception";
+        }
+        return ret;
+    }
+}
+
 App::DocumentObjectExecReturn *DrawView::execute()
 {
 //    Base::Console().message("DV::execute() - %s touched: %d\n", getNameInDocument(), isTouched());

src/Mod/TechDraw/App/DrawView.h

@@ -65,6 +65,7 @@ public:
 
     /** @name methods override Feature */
     //@{
+    App::DocumentObjectExecReturn* recompute() override;
     /// recalculate the Feature
     App::DocumentObjectExecReturn *execute() override;
     void onDocumentRestored() override;

src/Mod/TechDraw/App/DrawViewPart.cpp

@@ -1537,6 +1537,8 @@ void DrawViewPart::handleChangedPropertyType(Base::XMLReader &reader, const char
         }
         return;
     }
+
+    DrawView::handleChangedPropertyType(reader, TypeName, prop);
 }
 
 // true if owner->element is a cosmetic vertex

src/Mod/TechDraw/App/DrawViewSection.cpp

@@ -1254,6 +1254,8 @@ void DrawViewSection::handleChangedPropertyType(Base::XMLReader &reader, const c
         }
         return;
     }
+
+    DrawViewPart::handleChangedPropertyType(reader, TypeName, prop);
 }
 
 // checks that SectionNormal and XDirection are perpendicular and that Direction is the same as