Reach sediments: avoid crash when trying to open Edit_reach_sediment_layer without any reach selected

src/View/MainWindow.py

@@ -1525,6 +1525,16 @@ class ApplicationWindow(QMainWindow, ListedSubWindow, WindowToolKit):
         sl.show()
 
     def open_reach_sediment_layers(self):
+        if self._study is None:
+            logger.debug(
+                "No study open for reach sediment layers edition..."
+            )
+            return
+
+        if not self._study.river.has_current_reach():
+            self.msg_select_reach()
+            return
+
         reach = self._study.river.current_reach().reach
 
         if self.sub_window_exists(