fix: Fix Tab not respecting background clearing

[Morphexe]

This fixes #183, although I am not 100% sure if this is the correct approach.

[Adanos020]

Hey, thanks for fixing this! I like how simple this is.

There is an even nicer way to do this: instead of making the fill color transparent, you can just replace the call to .rect with .rect_stroke and remove the color argument.

[Morphexe]

Yeah, I am still learning the libs around, and I wasn`t sure of what I was doing - literally picked up rust yesterday lol.

[Adanos020]

You're clearly doing great since you've been able to identify and fix the issue rather quickly!