Fix 1675309: CanvasView::close() was previously just hiding the canvas, not closing it.
drwxr-xr-x - ETL
drwxr-xr-x - autobuild
drwxr-xr-x - gtkmm-osx
drwxr-xr-x - synfig-core
drwxr-xr-x - synfig-osx
drwxr-xr-x - synfig-studio