Crop tool doesn't work anymore

## Crop Tool in Drawing 1.0.2-1build1 doesn't work properly

### Problem

When using the Crop Tool in Drawing, you can only slide the right border to the middle and the lower border to the middle. Sliding the upper border to the middle and the left border to middle doesn't work anymore.

In the FORMER version of Drawing, version 1.0.2 (without build designation, 5089 Kb) presented in Linux Mint Cinnamon 21.3 (DE=6.0.4), the Crop Tool worked perfectly.

### Steps to reproduce the bug

1. Open a PNG to edit
2. Click the [Crop] icon in the left toolbar or use [Menu Tools\Active Tool\Crop]
3. Slide the right border to the middle > OK
4. Slide the lower border to the middle > OK
5. Slide the UPPER border to the middle > the LOWER border moves > this does not work properly
6. Slide the LEFT border to the middle > the RIGHT border moves > this does not work properly

### System

- Device: desktop computer
- OS: Linux Mint Cinnamon 22
- Desktop environment: Cinnamon 6.2.7
- Package format: unknown
- App version: 1.0.2-1build1
- Size: 5135 kB

Reproduce the Crop Tool issue using the listed steps with a PNG on Linux Mint Cinnamon 22, then inspect the crop tool's handling of the upper and left borders. Compare those behaviors with the working version described in the report; done means all four borders can be moved independently and the resulting crop is correct.

Written by the indexing model from the issue text.