I noticed the exact same issue, very annoying. It's hard to say if it's an Apple bug or Sublime. Apple induced the issue, but Sublime is the only app that seems to be affected on my system, so my guess is that there's a new API or something rolled out in 10.12.5 for apps to launch browsers and Sublime doesn't support the new code or something. Hopefully it gets fixed soon by whoever.
Interestingly mine was opening FireFox (which I have loaded but never use). So I deleted Firefox but now it only opens Safari. Apparently it hates Chrome! LOL