Made the house number generator use a join on the random length list of #

Without the join, it will just call ToString(), which gives something
along the lines of:
Faker.Extensions.NumberExtensions+<Times>d__5`1[System.String]275 Salma
Divide Suite 548 for a US street address.
Additionally the Join is changes to return the empty string in case the
IEnumerable is empty (it crashes otherwise)