Menus: Hide bulk-select options when no menus exist

[dlh]

The new "Bulk Select" checkbox and "Remove Selected Items" button are shown to the user even when no menus exist and the user is being invited to create their first menu.

Arguably, the new checkbox and button look somewhat awkward next to the "Give your menu a name..." instructions, and they conflict with the fact that the meta boxes for adding new items are disabled when no menus exist.

While the new checkbox and button are also visible when a menu exists but has no items, their being visible in that case is at least a little more consistent with the bulk-select checkbox on post list tables, which is also visible when the list table has no rows.

The linked PR would hide the bulk-select options when no menus exist, but a case could be made for disabling them instead to match the add-new meta boxes.

Trac ticket: https://core.trac.wordpress.org/ticket/53654

[sabernhardt]

The patch looks good. Since RC4 was already packaged, I'll put this in the 5.8.1 milestone.

[peterwilsoncc]

LGTM, thanks David and Stephen.

[peterwilsoncc]

In 51539:

Menus: Hide bulk-select on new menu page.

Prevent the bulk-select option from displaying when adding a new menu. This also prevents the option from displaying when an administrator first visits the menu page and no menus are set.

Props dlh, sabernhardt.
Fixes #53654.

[peterwilsoncc]

Reopening for merging to the 5.8 branch.

[desrosj]

In 51596:

Menus: Hide bulk-select on new menu page.

Prevent the bulk-select option from displaying when adding a new menu. This also prevents the option from displaying when an administrator first visits the menu page and no menus are set.

Props dlh, sabernhardt, peterwilsoncc.
Merges [51539] to the 5.8 branch.
Fixes #53654.