Custom scale can be 0 or NaN

[CappaBot1]

You can set the custom scale to 0 or leave it empty and press the Save as PNG button.
Setting the custom scale to NaN saves it at 1 scale as 300x150 but setting it to 0 saves an empty file.
I would fix this but I don't know how :)

[andreMc05]

I have a fix for this issue. I don't know how you want me to push it and create the PR. Do I push my branch, create the PR, and then delete my branch?

[CappaBot1]

idk, I'm kinda new to github