[GUI] Duplicate drawing in the depot dialog

[Ranran]

The top part of the depot dialog appears to display the same content twice or more in duplicate.
(I'm not sure if the previous bug was related to this, the bug that existed before was that every time you clicked on the dialog, the upper layer would be duplicated.)
This is clarified by the transparency of the pixels. Duplicate display is performed in both the vehicle bar legend display and the vehicle list display.
For example, look carefully at the edges of the vehicle's roof and the outline of the upgrade symbol in the legend.
You can see that the image is duplicated and transparency is lost.

[jamespetts]

Thank you for the report. Can I check whether this is still reproducible? I have not worked on the GUI code a great deal (and not much at all since all of your excellent improvements in the last few years), so I am not familiar with the code in which this issue arises.

[Ranran]

I believe this bug will be resolved by pull request #546.