是什么原因导致了这个领域的崩溃?

我有一个非常偶然的领域崩溃,我自己无法复制。

崩溃日志的回溯顶部如下所示:

Exception Type:  EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note:  EXC_CORPSE_NOTIFY
Triggered by Thread:  0

Last Exception Backtrace:
0   CoreFoundation                  0x181832d8c __exceptionPreprocess + 228 (NSException.m:166)
1   libobjc.A.dylib                 0x1809ec5ec objc_exception_throw + 56 (objc-exception.mm:521)
2   Realm                           0x10061e858 invocation function for block in objc_object* (anonymous namespace)::makeBoxedGetter<realm::StringData>(unsigned long) + 304 (RLMObject_Private.hpp:45)
3   My App                          0x1001c239c DetailViewController.getTheTitleOfCaller() + 64 (DetailViewController.swift:1863)

getTheTitleOfCaller()方法如下所示。

func getTheTitleOfCaller() -> String
    {
        var theTitle: String = ""
        if self.caller?.name != nil
        {
            theTitle = (self.caller?.name)!
        }
        else
        {
            theTitle = "Default title"
        }
        return theTitle
}

invocation function for block in objc_object* (anonymous namespace)::makeBoxedGetter<realm::StringData>

或者知道是什么导致了这个例外?