Randomly pull from list of shelters.

Not sure if you agree to handle it this way, but it looks like the APIs don't support including results from multiple shelters at least with the pieces of the APIs utilized? 

It creates an array from comma separated shelter ids then randomly chooses from the array. If there's just a single entry, it will only use the given entry.
You can call #split then #sample on a empty or non-comma separated string. There's no need to have any conditional checks.