You cannot remove every risk from every situation.
I would wager that the kids who end up stabbed are the ones who are in the gangs / hanging around with people who carry knives.
That would drastically reduce the risk of one of your kids being involved in something like that.
Mugging - admittedly that’s more likely to be a genuine risk but you can’t keep them chaperoned for ever and maybe you need to accept that At some point something bad is going to happen to them - that’s life - that’s how you learn, how you build resilience etc
Apart from locking them up forever, what can you realistically do to
a) reduce the chances of them being mugged
b) reduce the impact if they are
So talk to them about awareness, trusting your instincts, not waving expensive phones around, keep valuables hidden / bags zipped shut, throwing items away from you then running rather than tussling over handbags, know how to lock / disable phones, spare keys available…
It sounds daft but I’d probably rather my kid got mugged when still living at home and I could immediately help deal with the emotional and practical fall out - rather than it happening for the first time when they were 18 and away at Uni. Then if it did happen when they were living independently they’d deal with it better.
If nothing bad ever happens to them, they won’t ever build the skills to deal with anything…