Crash only caused since iOS13 which I can't reproduce

Crashlytics has been registering this crash which I can't seem to reproduce. I have looked at the code and I can't find anything that could cause this crash.

What is stranger is that it has only been showing up since the release of iOS13. All the crashes are on devices that have iOS13 installed. Prior to iOS13 this crash never happend. This particular piece of code has been there for over two years.

Can anyone come up with what might be causing this?

Thanks in advance.

Crashed: com.apple.main-thread
0  Spotted by                     0x104eaf2c0 partial apply for closure #1 in CitiesListViewController.tableSections.didset + 35 (CitiesListViewController.swift:35)
1  Spotted by                     0x104ee8508 thunk for @escaping @callee_guaranteed () -> () (<compiler-generated>)
2  libdispatch.dylib              0x1b48b1610 _dispatch_call_block_and_release + 24
3  libdispatch.dylib              0x1b48b2184 _dispatch_client_callout + 16
4  libdispatch.dylib              0x1b489535c _dispatch_main_queue_callback_4CF$VARIANT$armv81 + 996
5  CoreFoundation                 0x1b4b623c4 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
6  CoreFoundation                 0x1b4b5d3b8 __CFRunLoopRun + 2004
7  CoreFoundation                 0x1b4b5c8bc CFRunLoopRunSpecific + 464
8  GraphicsServices               0x1be9c8328 GSEventRunModal + 104
9  UIKitCore                      0x1b8bf26d4 UIApplicationMain + 1936
10 Spotted by                     0x104e95c00 main + 21 (SBLAppDelegate.swift:21)
11 libdyld.dylib                  0x1b49e7460 start + 4

This is the code I have (line 35 is self.tableView.reloadData()):

typealias TableData = [SectionData]
typealias SectionData = [String: [Any]]

private var tableSections = TableData() {
    didSet {
        DispatchQueue.main.async {
            self.tableView.reloadData()
        }
    }
}

The datasource code:

func setupData() {
    let sortPurchasedCitiesByAlpha: (CityID, CityID) -> Bool = { (cityId1, cityId2) -> Bool in
        guard
            let city1 = CitiesManager.shared.city(withId: cityId1),
            let city2 = CitiesManager.shared.city(withId: cityId2)
            else { assertionFailure("missing cities?"); return false }
        return city1.name.lowercased() <= city2.name.lowercased()
    }
    var sections = TableData()
    // reverse to show most recent purchase first
    let allPurchased = Array(CitiesManager.shared.purchasedCityIds())
    var purchased: [CityID] = []
    let lastUsedCityId = Defaults[.lastUsedCity]
    if let lastUsedCityId = lastUsedCityId {
        // put last used first
        let rest = Array(allPurchased.removing(lastUsedCityId))
        let restSorted = rest.sorted(by: sortPurchasedCitiesByAlpha)
        if allPurchased.contains(lastUsedCityId) { // may have been deleted
            purchased.append(lastUsedCityId)
        }
        purchased.append(contentsOf: restSorted)
    } else {
        purchased = allPurchased.sorted(by: sortPurchasedCitiesByAlpha)
    }
    installedSectionPresent = !purchased.isEmpty
    if installedSectionPresent {
        sections.append(["Installed": purchased])
    }
    let continents = CitiesManager.shared.allContinentsOfNotPurchasedCities()
    continents.forEach { continent in
        let cityIds = CitiesManager.shared.cityIdsNotPurchased(forContinent: continent)
        sections.append([continent: cityIds])
    }
    tableSections = sections
}