I'm only seeing it on a single machine at work, but please take the time to see if you can reproduce it. perhaps it's just that one machine. I waited for 48.1 just to be sure it's not already solved but it seems like I still have this problem:

When I create a new file and then attempt to save it, I have to explicitly add the "svg" extension. If I don't, the file is saved without an extension.

Another issue I see on all both home and office machines: When I do a "Save As...", the save dialog opens with the file name field empty, when in most other applicatios it contains the current file name.

Both issues are on Windows, I haven't tested on my Linux partition yet.