Restore the ViewObject

I think we need to restore the ViewObject in such cases. I assume this problems exists for all Draft and BIM objects. So this commit is just an example implementation.

src/Mod/Draft/draftobjects/draft_annotation.py

@@ -59,12 +59,12 @@ class DraftAnnotation(object):
         Check if new properties are present after the object is restored
         in order to migrate older objects.
         """
-        if not hasattr(obj, "ViewObject"):
+        if not getattr(obj, "ViewObject", None):
             return
         vobj = obj.ViewObject
-        if not vobj:
-            return
         if not getattr(vobj, "Proxy", None):
+            # Object was save without GUI.
+            # onDocumentRestored in the object class should restore the ViewObject.
             return
         if hasattr(vobj, "ScaleMultiplier") and hasattr(vobj, "AnnotationStyle"):
             return