Saving as .puffin _sometimes_ breaks

[emilk]

My repro: connect puffin_viewer to a server with --url 127.0.0.1:8585, hit save, then try to load the saved .puffin in a new puffin_viewer process.

This sometimes works, but sometimes I end up with a broken .puffin file, like this:

broken.puffin.zip

• Probably broke in Stream scope information only once #169
• Maybe related to Wrong scope descriptions in puffin viewer when running profiled program multiple times #200 ?

[gwen-lg]

I have probably identified the source of the problem. I can't work on in in the next 2 days, but after I will take a look at #200 to see if there is a common origin, and work on fixes and code improvement in a direction that suits both.