guiSetAlpha does not affect edit box caret

[qaisjp]

Describe the bug
Changing the alpha of an edit box does not affect its caret and does not allow the cursor to blink.

To Reproduce
Steps to reproduce the behavior:

1. crun edit = guiCreateEdit(500,500,100,20,"",false)
2. Click the edit.
3. crun guiSetAlpha(edit,0.2)
4. You will see the edit caret is still 100% alpha.
5. crun guiSetAlpha(edit,0) will not have any effect on edit caret.

Expected behavior
The alpha of the caret should be equal to the alpha of the edit box.

Additional context
From https://bugs.mtasa.com/view.php?id=9306

[Lpsd]

I don't think it's possible to set the alpha of the caret in CEGUI 0.4.0 - iirc there is no property for it within CEGUI.

It's possible in 0.8.7, so will be resolved with #1459