[Form]: theme switch failure during form editing

## Description
There is an issue where the theme doesn't switch correctly when a user attempts to edit a row and selects a different theme.

## Steps to Reproduce
1. Open [Demo->Form](https://uui.epam.com/demo?id=form).
2. Edit any row.
3. Switch to other theme.

## Actual result
The theme doesn't switch as expected.

https://github.com/user-attachments/assets/af9e014d-ffb7-46de-b5d8-f4c200cd4ab4

## Expected result
When editing rows a modal warning about unsaved changes ("Your data may be lost. Do you want to save data?") should appear and remain visible long enough for the user to make a decision. After interacting with this modal, whether choosing to save or discard changes, the theme should then switch seamlessly according to the user's selection.

## Environment
* UUI version: 5.10.1
* Browser name: any
* Operating System: any