Minor refactoring

SignalServiceKit/src/Loki/Protocol/Session Management/SessionManagementProtocol.swift

@@ -62,7 +62,8 @@ public final class SessionManagementProtocol : NSObject {
 
     @objc(shouldUseFallbackEncryptionForMessage:recipientID:transaction:)
     public static func shouldUseFallbackEncryption(for message: TSOutgoingMessage, recipientID: String, transaction: YapDatabaseReadWriteTransaction) -> Bool {
-        if message is SessionRequestMessage { return true }
+        if SharedSenderKeysImplementation.shared.isClosedGroup(recipientID) { return true } // We don't actually use fallback encryption but this indicates that we don't need a session
+        else if message is SessionRequestMessage { return true }
         else if let message = message as? DeviceLinkMessage, message.kind == .request { return true }
         else if message is OWSOutgoingNullMessage { return false }
         return !storage.containsSession(recipientID, deviceId: Int32(OWSDevicePrimaryDeviceId), protocolContext: transaction)