[8.x] Avoid no-op database query in Model::destroy() with empty ids

[spawnia]

I recently discovered that calling Model::destroy() with an empty array produces an unnecessary no-op database query.

select * from `tasks` where 0 = 1

This happens because the destroy() method calls Builder::whereIn(), which in turn turn an empty set of ids into the condition 0 = 1:

framework/src/Illuminate/Database/Query/Grammars/Grammar.php

Line 271 in 5ba7984

return '0 = 1';

Since I do not know the reasons for adding the 0 = 1 condition, I went for a more cautious and minimal change.

Now, destroy() checks for an empty input and bails early, saving a database roundtrip for a query that is guaranteed to have no effect.