NRE when master node cannot be obtained during Observe

Unhandled Exception: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object.[0;39m
[709.94 INFO] (LineGobbler doFilter:115) [39m+++ Following exception has internal ID: 1[0;39m
[709.94 INFO] (SDKD log:137) [39m at Couchbase.Core.Buckets.KeyObserver.<>c_DisplayClass6.<<ObserveAsync>b1>d_b.MoveNext() in c:\jenkins\workspace\situational-net\centos006-cbsdk-win8-net-client2\couchbase-net-client\Src\Couchbase\Core\Buckets\KeyObserver.cs:line 185[0;39m
[709.94 INFO] (SDKD log:137) [39m--- End of stack trace from previous location where exception was thrown ---[0;39m
[709.94 INFO] (LineGobbler doFilter:115) [39m+++ Following exception has internal ID: 3[0;39m
[709.94 INFO] (SDKD log:137) [39m at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()