Is removing elements of AA in foreach loop safe?

[berni via Digitalmars-d-learn]

Iterating of some structure and removing elements thereby is 
always errorprone and should be avoided. But: In case of AA, I've 
got the feeling, that it might be safe:

foreach (k,v;ways)
    if (v.empty)
        ways.remove(k);

Do you agree? Or is there a better way to achieve this?