Issue #2173 fixed

- on_selection_changed is issued on "del"
- it is also issued on "reduce selection to highlighted ones" in property dialog

src/laybasic/laybasic/layEditable.cc

@@ -110,6 +110,8 @@ Editables::del (db::Transaction *transaction)
         e->del ();
       }
 
+      signal_selection_changed ();
+
     } catch (...) {
       trans_holder->cancel ();
       throw;

src/layui/layui/layPropertiesDialog.cc

@@ -341,6 +341,8 @@ BEGIN_PROTECTED
 
   //  confine the selection
 
+  auto prev_selected = mp_editables->selection_size ();
+
   mp_tree_model->begin_reset_model ();
 
   auto selection = mp_ui->tree->selectionModel ()->selectedIndexes ();
@@ -409,6 +411,10 @@ BEGIN_PROTECTED
 
   update_controls ();
 
+  if (m_objects != prev_selected) {
+    mp_editables->signal_selection_changed ();
+  }
+
 END_PROTECTED
 }