System Information
Operating system: windows 10
Graphics card: GIGABYTE NVIDIA GeForce RTX 2070

Blender Version

Worked: 2.90.0

Short description of error
Blender crashes every time I put a driver that copy the x scale (or y or z) of an object to another one.

Exact steps for others to reproduce the error

++I cannot attach my file it's too big++

I select the object, add the driver on the scale (x, y or z). The quick driver window appears, but an error message appears the next second 'invalid python expression', even though I didn't do anything yet.
Then I try to click on the pipette to select an object but nothing happens / it looks buggy.
Then I go to the driver editor, the pipette works there, but after clicking the pipette, if I try to input an expression Blender crashes.
(The same happens in the quick driver window)

My workaround is to fill the input variable, copy it, delete it, not fill the expression.
Then re-edit the driver paste the variable, then edit the expression.

I tried to redo the same thing with the location and the rotation, even though the pipette was still buggy, I couldn't reproduce the bug

Let me know if I can help more