Adcolony sdk Fatal Exception

Fatal Exception: java.lang.NullPointerException
Attempt to invoke interface method 'void java.util.concurrent.ExecutorService.shutdown()' on a null object reference
    com.adcolony.sdk.ac.b (SourceFile:143)
    com.adcolony.sdk.ao.b (SourceFile:214)
    com.adcolony.sdk.ao.run (SourceFile:145)
    java.lang.Thread.run (Thread.java:762)