One more fix to updates of the "Slice now" and "Export G-code buttons"

- "Sliced now" button is hidden when "Background process" is selected
- deleted extra enable_buttons() function call

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -263,7 +263,6 @@ void ObjectList::selection_changed()
         event.SetEventObject(this);
         wxPostEvent(this, event);
     }
-    wxGetApp().sidebar().enable_buttons(!m_objects_model->IsEmpty());
 
     part_selection_changed();
 

src/slic3r/GUI/MainFrame.cpp

@@ -766,7 +766,9 @@ void MainFrame::on_value_changed(wxCommandEvent& event)
 // Update the UI based on the current preferences.
 void MainFrame::update_ui_from_settings()
 {
-    m_menu_item_reslice_now->Enable(wxGetApp().app_config->get("background_processing") == "1");
+    bool bp_on = wxGetApp().app_config->get("background_processing") == "1";
+    m_menu_item_reslice_now->Enable(bp_on);
+    m_plater->sidebar().show_button(baReslice, !bp_on);
     if (m_plater)
         m_plater->update_ui_from_settings();
     for (auto tab: wxGetApp().tabs_list)

src/slic3r/GUI/Plater.cpp

@@ -1814,8 +1814,6 @@ unsigned int Plater::priv::update_background_process()
         // Some previously calculated data on the Print was invalidated.
         // Hide the slicing results, as the current slicing status is no more valid.
         this->sidebar->show_sliced_info_sizer(false);
-        // Disable buttons during background process.
-        this->sidebar->enable_buttons(false);
         // Reset preview canvases. If the print has been invalidated, the preview canvases will be cleared.
         // Otherwise they will be just refreshed.
         this->gcode_preview_data.reset();
@@ -2059,7 +2057,6 @@ void Plater::priv::on_process_completed(wxCommandEvent &evt)
 		this->statusbar()->set_status_text(L("Cancelled"));
 
     this->sidebar->show_sliced_info_sizer(success);
-    this->sidebar->enable_buttons(success);
 
     // This updates the "Slice now", "Export G-code", "Arrange" buttons status.
     // Namely, it refreshes the "Out of print bed" property of all the ModelObjects, and it enables