我很难看到这个'（null）'实体参与其中的位置。通过我所有的绑定设置，CoreData模型，检查文档等不知道。 控制台即将推出：
2013-10-10 19：41：44.666 BusinessDesk [17180：303]无法执行操作，因为无法找到名称为“（null）”的实体
2013-10-10 19：41：44.673 BusinessDesk [17180：303]（
0 CoreFoundation 0x00007fff8db8741c __exceptionPreprocess + 172
1 libobjc.A.dylib 0x00007fff930d6e75 objc_exception_throw + 43
2 CoreFoundation 0x00007fff8db872cc +[NSException raise:format:] + 204
3 AppKit 0x00007fff93b0c3a8 -[_NSManagedProxy _entity] + 141
4 AppKit 0x00007fff93b0c265 -[_NSManagedProxy fetchRequestWithSortDescriptors:limit:] + 95
5 AppKit 0x00007fff93d5c40a -[_NSManagedProxy _storesDidChange:] + 125
6 CoreFoundation 0x00007fff8db55fcc __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 12
7 CoreFoundation 0x00007fff8da49c5d _CFXNotificationPost + 2893
8 Foundation 0x00007fff948994aa -[NSNotificationCenter postNotificationName:object:userInfo:] + 68
9 CoreData 0x00007fff926aa6ad -[NSPersistentStoreCoordinator(_NSInternalMethods) _postStoresChangedNotificationsForStores:changeKey:options:] + 253
10 CoreData 0x00007fff9269aea6 -[NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:] + 2342
11 AppKit 0x00007fff93d7a549 -[NSPersistentDocument configurePersistentStoreCoordinatorForURL:ofType:modelConfiguration:storeOptions:error:] + 1268
12 AppKit 0x00007fff940209a1 -[NSPersistentDocument(NSDeprecatedInternal) _configurePersistentStoreCoordinatorForURL:ofType:error:] + 156
13 AppKit 0x00007fff93d7ad1c -[NSPersistentDocument writeToURL:ofType:forSaveOperation:originalContentsURL:error:] + 818
14 AppKit 0x00007fff93c11a2f -[NSDocument _writeSafelyToURL:ofType:forSaveOperation:forceTemporaryDirectory:error:] + 339
15 AppKit 0x00007fff93c1259c -[NSDocument _writeSafelyToURL:ofType:forSaveOperation:error:] + 28
16 AppKit 0x00007fff93c12709 -[NSDocument writeSafelyToURL:ofType:forSaveOperation:error:] + 356
17 AppKit 0x00007fff93d7c283 -[NSPersistentDocument writeSafelyToURL:ofType:forSaveOperation:error:] + 601
18 AppKit 0x00007fff93c1d58c __66-[NSDocument saveToURL:ofType:forSaveOperation:completionHandler:]_block_invoke_22042 + 76
19 AppKit 0x00007fff93c1e877 __66-[NSDocument saveToURL:ofType:forSaveOperation:completionHandler:]_block_invoke_22125 + 248
20 AppKit 0x00007fff93c1e770 __66-[NSDocument saveToURL:ofType:forSaveOperation:completionHandler:]_block_invoke2122 + 341
21 AppKit 0x00007fff93c1d480 __66-[NSDocument saveToURL:ofType:forSaveOperation:completionHandler:]_block_invoke2033 + 1501
22 Foundation 0x00007fff949449f9 -[NSFileCoordinator(NSPrivate) _invokeAccessor:orDont:thenRelinquishAccessClaimForID:] + 224
23 Foundation 0x00007fff94ab7637 -[NSFileCoordinator(NSPrivate) _coordinateWritingItemAtURL:options:error:byAccessor:] + 702
24 AppKit 0x00007fff93c1915f -[NSDocument _fileCoordinator:coordinateReadingContentsAndWritingItemAtURL:byAccessor:] + 421
25 AppKit 0x00007fff93c1c7a4 __66-[NSDocument saveToURL:ofType:forSaveOperation:completionHandler:]_block_invoke + 599
26 AppKit 0x00007fff93c0a595 -[NSDocument continueFileAccessUsingBlock:] + 234
27 AppKit 0x00007fff93c0aa2d -[NSDocument _performFileAccessOnMainThread:usingBlock:] + 782
28 AppKit 0x00007fff93c0b6b4 -[NSDocument performAsynchronousFileAccessUsingBlock:] + 481
29 AppKit 0x00007fff93c1c53e -[NSDocument saveToURL:ofType:forSaveOperation:completionHandler:] + 148
30 AppKit 0x00007fff93c1895f __85-[NSDocument saveToURL:ofType:forSaveOperation:delegate:didSaveSelector:contextInfo:]_block_invoke_2 + 310
31 AppKit 0x00007fff93c45910 -[NSDocument _commitEditingThenContinue:] + 501
32 AppKit 0x00007fff93d79661 __62-[NSPersistentDocument _documentEditor:didCommit:withContext:]_block_invoke + 53
33 CoreFoundation 0x00007fff8dab87cc __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
34 CoreFoundation 0x00007fff8daa9ee5 __CFRunLoopDoBlocks + 341
35 CoreFoundation 0x00007fff8daa9c6e __CFRunLoopRun + 1982
36 CoreFoundation 0x00007fff8daa9275 CFRunLoopRunSpecific + 309
37 HIToolbox 0x00007fff8d722f0d RunCurrentEventLoopInMode + 226
38 HIToolbox 0x00007fff8d722b85 ReceiveNextEventCommon + 173
39 HIToolbox 0x00007fff8d722abc _BlockUntilNextEventMatchingListInModeWithFilter + 65
40 AppKit 0x00007fff9379f28e _DPSNextEvent + 1434
41 AppKit 0x00007fff9379e8db -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 122
42 AppKit 0x00007fff937929cc -[NSApplication run] + 553
43 AppKit 0x00007fff9377d803 NSApplicationMain + 940
44 BusinessDesk 0x000000010000b3d2 main + 34
45 libdyld.dylib 0x00007fff907fa5fd start + 1
）
有人对这个问题有所了解吗？