objective c - (CarbonCore.framework) FSEventStreamFlushSync(): failed assertion '(SInt64)last_id > 0LL' -

i'm use library cdevents monitor file system.

when calling method flash synchronously

- (void)flushsynchronously {     fseventstreamflushsync(_eventstream); } 

get message

(carboncore.framework) fseventstreamflushsync(): failed assertion '(sint64)last_id > 0ll' 

here method signature fseventstreamflushsync() fsevents.h

/*  *  fseventstreamflushsync()  *    *  discussion:  *    asks fs events service flush out events have  *    occurred have not yet been delivered, due latency  *    parameter supplied when stream created.   *    flushing occurs synchronously -- time call returns,  *    callback have been invoked every event had  *    occurred @ time made call.  *    fseventstreamflushsync() can called after stream has  *    been started, via fseventstreamstart().  *    *  parameters:  *      *    streamref:  *      valid stream.  *    *  availability:  *    mac os x:         in version 10.5 , later in coreservices.framework  *    carbonlib:        not available  *    non-carbon cfm:   not available  */ extern void  fseventstreamflushsync(fseventstreamref streamref)            __osx_available_starting(__mac_10_5, __iphone_na);