Inconsistent new item priority assignment logic [5.2.1]

Each section (page/category) has an order associated with it to allow quick and easy way of positioning it in the Front-End menu:

When adding new item it's possible to change it's order as desired, but by default it's placed in the end of the list.

Steps to Reproduce the Problem

1. open new section creation window by clicking on "New Section" toolbar button
2. enter section name (the only required field by the way)
3. confirm, that:
   1. there are 9th entries in Order dropdown
   2. the 9th order is selected for this section
4. select another order (e.g. 5th)

After this the 9th position would disappear from the list and it's now impossible to place new section at the end of the list and user is forced to place it in between 2 other sections.

Solution

While operation on item from temp table, that wasn't yet saved to live table (has ID <= 0) we need to always add that 9th order entry.

Related Tasks

INP-1412 - Getting issue details... STATUS