Web console: grid-showing-rows component in grids with no selection

The issue:
Changes to grid-showing-rows component introduced by IGNITE-9981 assume that all grid instances have selection module enabled. This is not true in some cases (see ui-grid/template.pug), which causes "can't access property of undefined" type of runtime errors.

What to do:
Handle missing selection API on grid instances in grid-showing-rows.