Fem: Update old ElementGeometry*D with new properties

src/Mod/Fem/femobjects/element_geometry1D.py

@@ -189,6 +189,8 @@ class ElementGeometry1D(base_femelement.BaseFemElement):
 
     def onDocumentRestored(self, obj):
         # update old project with new properties
+        super().onDocumentRestored(obj)
+
         for prop in self._get_properties():
             try:
                 obj.getPropertyByName(prop.name)

src/Mod/Fem/femobjects/element_geometry2D.py

@@ -30,6 +30,7 @@ __url__ = "https://www.freecad.org"
 #  \brief element geometry 2D object
 
 from . import base_femelement
+from .base_fempythonobject import _PropHelper
 
 
 class ElementGeometry2D(base_femelement.BaseFemElement):
@@ -42,18 +43,30 @@ class ElementGeometry2D(base_femelement.BaseFemElement):
     def __init__(self, obj):
         super().__init__(obj)
 
-        obj.addProperty(
-            "App::PropertyLength",
-            "Thickness",
-            "ShellThickness",
-            "set thickness of the shell elements",
-        )
-        obj.setPropertyStatus("Thickness", "LockDynamic")
+    def _get_properties(self):
+        prop = super()._get_properties()
 
-        obj.addProperty(
-            "App::PropertyFloat",
-            "Offset",
-            "ShellThickness",
-            "set thickness offset of the shell elements",
+        prop.append(
+            _PropHelper(
+                type="App::PropertyLength",
+                name="Thickness",
+                group="ShellThickness",
+                doc="Set thickness of the shell elements",
+                value="0 mm",
+            )
         )
-        obj.Offset = 0.0
+        prop.append(
+            _PropHelper(
+                type="App::PropertyFloat",
+                name="Offset",
+                group="ShellThickness",
+                doc="Set thickness offset of the shell elements",
+                value=0.0,
+            )
+        )
+
+        return prop
+
+    def onDocumentRestored(self, obj):
+        # update old project with new properties
+        super().onDocumentRestored(obj)