Fixed crash when notification key or value is nil

I got a couple of crashes like this in Crashlytics.

Fatal Exception: NSInvalidArgumentException
*** setObjectForKey: object cannot be nil (key: UIApplicationLaunchOptionsURLKey)

    Thread : Fatal Exception: NSInvalidArgumentException
    0  CoreFoundation                 0x2da69f83 __exceptionPreprocess + 130
    1  libobjc.A.dylib                0x38663ccf objc_exception_throw + 38
    2  CoreFoundation                 0x2d9a58f3 -[__NSDictionaryM setObject:forKey:] + 818
    3  Tablet CMD                     0x00369703 __47-[Antenna startLoggingNotificationName:object:]_block_invoke_2 (Antenna.m:201)
    4  CoreFoundation                 0x2d9a6043 __65-[__NSDictionaryM enumerateKeysAndObjectsWithOptions:usingBlock:]_block_invoke + 98
    5  CoreFoundation                 0x2d9a5f67 -[__NSDictionaryM enumerateKeysAndObjectsWithOptions:usingBlock:] + 162
    6  Tablet CMD                     0x00369609 __47-[Antenna startLoggingNotificationName:object:]_block_invoke (Antenna.m:200)
    7  Tablet CMD                     0x00369b11 __76-[Antenna startLoggingNotificationName:object:constructingPayLoadFromBlock:]_block_invoke (Antenna.m:219)
    8  Foundation                     0x2e38e487 -[__NSObserver _doit:] + 290
    9  CoreFoundation                 0x2da2c1a1 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 12
    10 Foundation                     0x2e3ae3c7 -[NSBlockOperation main] + 130
    11 Foundation                     0x2e39e5ab -[__NSOperationInternal _start:] + 770
    12 Foundation                     0x2e44276d __NSOQSchedule_f + 60
    13 libdispatch.dylib              0x38b51293 _dispatch_async_redirect_invoke$VARIANT$mp + 110
    14 libdispatch.dylib              0x38b52ad7 _dispatch_root_queue_drain + 222
    15 libdispatch.dylib              0x38b52d29 _dispatch_worker_thread2 + 56
    16 libsystem_pthread.dylib        0x38c8dbd3 _pthread_wqthread + 298
    17 libsystem_pthread.dylib        0x38c8da98 start_wqthread + 8