Sorting / Filtering bug for removed column

[DGStefan]

When you have filtered on a column and remove the column, it is not visible that sorting is still done on the removed column. You will get no results when you filter afterwards on another column. The only indication that there is sorted in that case, is because you can see the 'reset sorting' button on top of the overview.

We should do a check if a column exists when sorting is still set as preference for a non existent column.

[tobiasschutter]

Check for array and if column exists (from orderby) on ACP_Sorting_Addon::get_sorting_preference