Catch null pointer exception when getting parts

And show an error message.  THere's not a lot we can do about it other than "there is a problem" but an error message is better than naught.
fix amber version for travis
Merge pull request #350 from nla/hr-null-pointer-error

Catch null pointer exception when getting children
Don't allow null credentials

We don't need to hit the UMS for null or empty credentials.
password and login fields required
Merge remote-tracking branch 'origin/master' into hr-cmstrs

* origin/master:
  password and login fields required
  Don't allow null credentials
  fix amber version for travis
  Catch null pointer exception when getting parts