BUG: always return the prediction brush (or mask) of the first bounding box

**Describe the bug**
A clear and concise description of what the bug is.
I want to get several masks from an image by adding several bounding boxes.

However, when I trying to do this in Label Studio, I found that: no matter how many boxes were drawn, the prediction returned would always related to the first box.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to an existing project.
2. Click on any image task. Turn on "Auto-Annotation" and "Auto-Accept Suggestions".
3. Click "Auto-detect" and choose "Rectangle Box". Draw a box, and wait for the prediction. If everything goes well, your will get a predicted mask.
4. Draw the another box, and wait for the prediction. Now, the bug is here: this returned mask corresponds to the first box but not the second box.

**Expected behavior**
The second predicted mask is expected to correspond to the second box.

**Environment (please complete the following information):**
- OS: [Ubuntu 22]
- Label Studio Version [1.12.1]

**Additional context**
If only one box exists, the prediction would always corresponds to that box. That is to say, we could get the right prediction by manually deleting the existed boxes before drawing a new one.