Fatal Exception: NSInvalidArgumentException
*** -[__NSDictionaryM setObject:forKeyedSubscript:]: key cannot be nil

-[RCPurchases purchaseProduct:withPayment:withPresentedOfferingIdentifier:completion:]

0  CoreFoundation                 0x19b5a096c __exceptionPreprocess
1  libobjc.A.dylib                0x19b2b9028 objc_exception_throw
2  CoreFoundation                 0x19b5f9500 -[__NSCFString characterAtIndex:].cold.1
3  CoreFoundation                 0x19b6035a0 -[__NSDictionaryM setObject:forKeyedSubscript:].cold.2
4  CoreFoundation                 0x19b47b190 -[__NSDictionaryM setObject:forKeyedSubscript:]
5  Purchases                      0x1054aa4b0 -[RCPurchases purchaseProduct:withPayment:withPresentedOfferingIdentifier:completion:] + 558 (RCPurchases.m:558)
6  Purchases                      0x1054a9f08 -[RCPurchases purchasePackage:withCompletionBlock:] + 485 (RCPurchases.m:485)
7  AppName                        0x104f2d738 closure #1 in RCPurchases.purchase(_:) + 134 (PurchasesExtension.swift:134)
8  AppName                        0x105055ee8 partial apply for thunk for @escaping @callee_guaranteed (@guaranteed @escaping @callee_guaranteed (@guaranteed SingleEvent<RCOfferings>) -> ()) -> (@out Disposable)
9  RxSwift                        0x1061c99f4 partial apply for closure #1 in static PrimitiveSequenceType<>.create(subscribe:) + 39 (Single.swift:39)
10 RxSwift                        0x10619946c AnonymousObservable.run<A>(_:cancel:) + 60 (Create.swift:60)
11 RxSwift                        0x1061a6f64 Producer.subscribe<A>(_:) + 18 (Producer.swift:18)
...