[REEF-1523] Fix Null Point exception in NameServer when message is null

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.16
• Assignee: Julia Wang
• Reporter: Julia Wang
• Created: 11/Aug/16 18:38
• Updated: 12/Aug/16 23:02
• Resolved: 12/Aug/16 23:02

Description

Currently, when communication between clinet and server is disconnected for whatever reason, mostly after a node is unregistered, the message received in NameServer is null. When we use message.Link, it causes null point exception, polluted the the driver log. We should handle this case instead of letting null point exception to throw.