Corrupt svg when saved

[hacklex]

After some manipulations I reached the state at which every saved file started with

<svg width="507.99999999999994" 
     height="507.99999999999994" 
     xmlns="http://www.w3.org/2000/svg" 
     version="1.1" 
     xml:space="preserve" 
     stroke="null">

which caused loading errors with some svg loaders, notably avalonia ui's Svg control.

Manipulations involved adding text layer and trying to convert it to path, then deleting it.

Resetting the image did not help.

Manually removing the stroke="null" fixed the issue of course, but still, as I think this info might help somebody else, I'm posting this issue here.