Roles are not deleted in the correct way, in the user zone.

[rafa31gz]

When adding roles to a user and want to delete them with the delete button, I noticed that this does not delete the row in the HTML, therefore sends an empty parameter and the server detects it as an SQL error.

General error: 1366 Incorrect integer value: '' for column 'role_id' at row 1 (SQL: insert into role_users (created_at, role_id, updated_at, user_id) values (2017-06-15 21:45:42, , 2017-06-15 21:45:42, 3))
app/sprinkles/admin/src/Controller/UserController.php(1147): Illuminate\Database\Eloquent\Relations\BelongsToMany->sync(Array)

[alexweissman]

It would appear that the row is being deleted, but then a "virgin row" is being added in its place with an empty value. The problem seems to be caused by @Silic0nS0ldier's rebase of the ufCollection widget. Apparently, the ! was dropped from the if condition in this block:
https://github.com/userfrosting/UserFrosting/blob/master/app/sprinkles/core/assets/local/core/js/uf-collection.js#L247-L253

It should read:

// If we're not using dropdowns, assert that the table doesn't already have a virgin row.  If not, create a new virgin row.
if (!this.settings.useDropdown) {
    var virginRows = this.settings.rowContainer.find('.uf-collection-row-virgin').length;
    if (!virginRows) {
        this._createVirginRow();
    }
}