Merge pull request #4698 from succhiello/feature/allow_deregister_without_ec2_elbs

add NoneType check.

library/cloud/ec2_elb

@@ -300,6 +300,7 @@ def main():
     elb_man = ElbManager(module, instance_id, ec2_elbs, aws_access_key,
                          aws_secret_key, region=region)
 
+    if ec2_elbs is not None:
         for elb in ec2_elbs:
             if not elb_man.exists(elb):
                 msg="ELB %s does not exist" % elb