主项目升级到Swift4，HandyJSON保持Swift3的情况下iOS 8.4闪退

我并不是很会看崩溃报告，不知道为啥最后崩溃在HandyJSON，iOS 8.4.1进入即闪退，导致我使用Bugly完全捕捉不到闪退信息，推测是初始化时模型化用户偏好中的用户数据导致的闪退。

0 libsystem_kernel.dylib 0x0000000197be7270 __pthread_kill + 8
1 libsystem_pthread.dylib 0x0000000197c8516c pthread_kill + 108
2 libsystem_c.dylib 0x0000000197b5eb14 abort + 108
3 libswiftCore.dylib 0x000000010160c560 0x101310000 + 3130720
4 libswiftCore.dylib 0x000000010160c514 0x101310000 + 3130644
5 libswiftCore.dylib 0x000000010160c868 0x101310000 + 3131496
6 HandyJSON 0x0000000100df7ca4 0x100dd8000 + 130212
7 HandyJSON 0x0000000100df7b3c 0x100dd8000 + 129852
8 HandyJSON 0x0000000100df7ec4 0x100dd8000 + 130756
9 HandyJSON 0x0000000100df869c 0x100dd8000 + 132764
10 HandyJSON 0x0000000100dfdf94 0x100dd8000 + 155540
11 HandyJSON 0x0000000100de63cc 0x100dd8000 + 58316
12 HandyJSON 0x0000000100de7f1c 0x100dd8000 + 65308
13 HandyJSON 0x0000000100de7c90 0x100dd8000 + 64656
14 zxtyjb-for-ios 0x00000001002dccac 0x1000f4000 + 2002092
15 zxtyjb-for-ios 0x0000000100239e38 0x1000f4000 + 1334840
16 zxtyjb-for-ios 0x0000000100239d5c 0x1000f4000 + 1334620
17 zxtyjb-for-ios 0x0000000100239e04 0x1000f4000 + 1334788
18 UIKit 0x000000018a1c8c14 -[UIViewController loadViewIfRequired] + 688
19 UIKit 0x000000018a1c8924 -[UIViewController view] + 28
20 UIKit 0x000000018a1cf160 -[UIWindow addRootViewControllerViewIfPossible] + 68
21 UIKit 0x000000018a1cc810 -[UIWindow _setHidden:forced:] + 256
22 UIKit 0x000000018a23e87c -[UIWindow makeKeyAndVisible] + 52
23 zxtyjb-for-ios 0x0000000100349ba8 0x1000f4000 + 2448296
24 zxtyjb-for-ios 0x0000000100347c34 0x1000f4000 + 2440244
25 zxtyjb-for-ios 0x00000001003490a0 0x1000f4000 + 2445472
26 UIKit 0x000000018a23b120 -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 400
27 UIKit 0x000000018a4527e4 -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 2372
28 UIKit 0x000000018a455198 -[UIApplication _runWithMainScene:transitionContext:completion:] + 1500
29 UIKit 0x000000018a453708 -[UIApplication workspaceDidEndTransaction:] + 180
30 FrontBoardServices 0x000000018df853c4 __31-[FBSSerialQueue performAsync:]_block_invoke_2 + 28
31 CoreFoundation 0x0000000185708278 __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 16
32 CoreFoundation 0x0000000185707380 __CFRunLoopDoBlocks + 308
33 CoreFoundation 0x00000001857059a4 __CFRunLoopRun + 1752
34 CoreFoundation 0x00000001856312d0 CFRunLoopRunSpecific + 392
35 UIKit 0x000000018a2343cc -[UIApplication _run] + 548
36 UIKit 0x000000018a22ef3c UIApplicationMain + 1484
37 zxtyjb-for-ios 0x0000000100351204 0x1000f4000 + 2478596
38 libdyld.dylib 0x0000000197acea04 start + 0

Start by reproducing the launch crash on iOS 8.4 with the main project on Swift 4 and HandyJSON on Swift 3. Trace the HandyJSON frames during user-preference model initialization and compare the compatibility boundary; done means the app no longer crashes on entry in that configuration.

Written by the indexing model from the issue text.