Editor: Sort problem in Objects table when few nested rows are added

Steps to reproduce:

Open Objects table

Open Npc record for editing

Add two or more rows to the Inventory table

Try to sort records in the table view by clicking on a column header (not ID). I tried Model, RecordType, Name, Script, Icon columns.

After that sorting doesn't applied and the exception is raised: "Trying to access non-existing column in the nested table!". But you can sort by ID. Also if the editor lost focus the sorting will be applied.

You can add rows into another nested table with the same result.

Sometimes the same exception is raised when you only add a nested row. In this case, the row may not be added to the nested table.

(RM-2611 from redmine: created on 2015-06-03 by Stanislav Bas, , closed on 2015-06-05 by cc 9cii)