I had started a response to this thread and then kicked the power button on my computer by mistake (it must be Monday) so here we go again.
The flip side of the issue of police telling women that they are basically asking for rape by dressing like "sluts" is that it gives the impression that if a woman dresses conservatively that she is not at risk of sexual assault. This can lead to a false sense of security and a lack of vigilance to her surroundings.
Women shouldn't HAVE to worry about how they dress and shouldn't HAVE to be concerned about walking alone at night (or hell, even during the day). Unfortunately that's not the world we live in. Sexual assault is a reality in our world. As such the police have a duty to warn women of the potential danger. But rather than victim blaming the better approach might be to reinforce staying as a group when out, not leaving your drinks unattended and letting someone know where you'll be and what time to expect you back.
Everything will be ok in the end. If it's not ok it's not the end.