crash in [FSEventsFilter users]

[Mike McCracken]

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[0]'
*** First throw call stack:
(
 0 CoreFoundation 0x00007fff9171cf56 __exceptionPreprocess + 198
 1 libobjc.A.dylib 0x00007fff8cefbdee objc_exception_throw + 43
 2 CoreFoundation 0x00007fff916c59f1 -[__NSPlaceholderArray initWithObjects:count:] + 113
 3 CoreFoundation 0x00007fff916daf91 +[NSArray arrayWithObjects:count:] + 49
 4 CoreFoundation 0x00007fff916fc940 -[NSDictionary allKeys] + 400
 5 com.ubuntu.one.fsevents 0x0000000100004bf6 -[FSEventsFilter users] + 54
 6 com.ubuntu.one.fsevents 0x0000000100003a3d -[FSEventDispatcher dispatchEvent:] + 141
 7 com.ubuntu.one.fsevents 0x0000000100004431 -[FSEventDispatcher run] + 961
 8 Foundation 0x00007fff8890372a -[NSThread main] + 68
 9 Foundation 0x00007fff889036a2 __NSThread__main__ + 1575
 10 libsystem_c.dylib 0x00007fff87e638bf _pthread_start + 335
 11 libsystem_c.dylib 0x00007fff87e66b75 thread_start + 13
)

terminate called throwing an exception
abort() called

Thread 0:: Dispatch queue: com.apple.main-thread
0 libsystem_kernel.dylib 0x00007fff8e8f167a mach_msg_trap + 10
1 libsystem_kernel.dylib 0x00007fff8e8f0d71 mach_msg + 73
2 com.apple.CoreFoundation 0x00007fff916a950c __CFRunLoopServiceMachPort + 188
3 com.apple.CoreFoundation 0x00007fff916b1c74 __CFRunLoopRun + 1204
4 com.apple.CoreFoundation 0x00007fff916b1486 CFRunLoopRunSpecific + 230
5 com.apple.Foundation 0x00007fff888b4f7b -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 267
6 com.apple.Foundation 0x00007fff888b4e67 -[NSRunLoop(NSRunLoop) run] + 62
7 com.ubuntu.one.fsevents 0x000000010000ac3c -[FSEventsDaemon application:runWithArguments:] + 1052 (FSEventsDaemon.m:286)
8 com.ubuntu.one.fsevents 0x000000010000b315 -[DDCliApplication runWithClass:] + 357 (DDCliApplication.m:76)
9 com.ubuntu.one.fsevents 0x000000010000b682 DDCliAppRunWithClass + 114 (DDCliApplication.m:113)
10 com.ubuntu.one.fsevents 0x0000000100001938 main + 56 (main.m:40)
11 com.ubuntu.one.fsevents 0x00000001000018f4 start + 52

Thread 1:: com.apple.CFSocket.private
0 libsystem_kernel.dylib 0x00007fff8e8f2df2 __select + 10
1 com.apple.CoreFoundation 0x00007fff916fac8b __CFSocketManager + 1355
2 libsystem_c.dylib 0x00007fff87e638bf _pthread_start + 335
3 libsystem_c.dylib 0x00007fff87e66b75 thread_start + 13

Thread 2:: Dispatch queue: com.apple.libdispatch-manager
0 libsystem_kernel.dylib 0x00007fff8e8f37e6 kevent + 10
1 libdispatch.dylib 0x00007fff90aec786 _dispatch_mgr_invoke + 923
2 libdispatch.dylib 0x00007fff90aeb316 _dispatch_mgr_thread + 54

Thread 3 Crashed:
0 libsystem_kernel.dylib 0x00007fff8e8f2ce2 __pthread_kill + 10
1 libsystem_c.dylib 0x00007fff87e657d2 pthread_kill + 95
2 libsystem_c.dylib 0x00007fff87e56a7a abort + 143
3 libc++abi.dylib 0x00007fff87b527bc abort_message + 214
4 libc++abi.dylib 0x00007fff87b4ffcf default_terminate() + 28
5 libobjc.A.dylib 0x00007fff8cefc249 _objc_terminate + 94
6 libc++abi.dylib 0x00007fff87b50001 safe_handler_caller(void (*)()) + 11
7 libc++abi.dylib 0x00007fff87b5005c std::terminate() + 16
8 libc++abi.dylib 0x00007fff87b51152 __cxa_throw + 114
9 libobjc.A.dylib 0x00007fff8cefbf0a objc_exception_throw + 327
10 com.apple.CoreFoundation 0x00007fff917a71b9 -[NSException raise] + 9
11 com.ubuntu.one.fsevents 0x000000010000451c -[FSEventDispatcher run] + 1196 (FSEventDispatcher.m:338)
12 com.apple.Foundation 0x00007fff8890372a -[NSThread main] + 68
13 com.apple.Foundation 0x00007fff889036a2 __NSThread__main__ + 1575
14 libsystem_c.dylib 0x00007fff87e638bf _pthread_start + 335
15 libsystem_c.dylib 0x00007fff87e66b75 thread_start + 13

Thread 4:
0 libsystem_kernel.dylib 0x00007fff8e8f3192 __workq_kernreturn + 10
1 libsystem_c.dylib 0x00007fff87e65594 _pthread_wqthread + 758
2 libsystem_c.dylib 0x00007fff87e66b85 start_wqthread + 13

Thread 5:
0 libsystem_kernel.dylib 0x00007fff8e8f3192 __workq_kernreturn + 10
1 libsystem_c.dylib 0x00007fff87e65594 _pthread_wqthread + 758
2 libsystem_c.dylib 0x00007fff87e66b85 start_wqthread + 13