HydraulicStructures: fix crash when selecting a rk before the reach

src/View/HydraulicStructures/Table.py

@@ -96,7 +96,8 @@ class ComboBoxDelegate(QItemDelegate):
             reach = self._data.hydraulic_structures\
                               .get(index.row())\
                               .input_reach
-            profiles = list(
+            # No reach selected yet: no profile to choose from
+            profiles = [] if reach is None else list(
                 filter(
                     lambda p: p.display_name() == text,
                     reach.reach.profiles