HS: Minor fix add method.

src/Model/HydraulicStructures/HydraulicStructures.py

@@ -24,6 +24,9 @@ from Model.Tools.PamhyrDB import SQLSubModel
 from Model.Except import NotImplementedMethodeError
 
 from Model.HydraulicStructures.Basic.HydraulicStructures import BasicHS
+from Model.HydraulicStructures.Basic.Types import (
+    NotDefined,
+)
 
 logger = logging.getLogger()
 
@@ -231,7 +234,7 @@ class HydraulicStructure(SQLSubModel):
         return self._data.copy()
 
     def add(self, index: int):
-        value = BasicHS(status=self._status)
+        value = NotDefined(status=self._status)
         self._data.insert(index, value)
         self._status.modified()
         return value