title: Cannot convert call result type '_?' to expected type '[UInt]'
body: <pre><code>self.mapper.identityIdsForQuickbloxUserIds(userIDs.map{($0 as! NSNumber).unsignedLongValue}, completion: { identityIdsMapping, error in
  </code></pre>
  
  <blockquote>
    <p>Cannot convert call result type '_?' to expected type '[UInt]'</p>
  </blockquote>
  
  <p><code>userIDs</code> is <code>NSSet</code></p>
  
  <p>and here is a function:</p>
  
  <pre><code>func identityIdsForQuickbloxUserIds(userIds:[UInt], completion:(identityIdsMapping:[UInt: String]?, error:NSError?) -&gt; Void)
  </code></pre>
  
  <p>how to convert it in a right way?</p>
  
  <p>This is external function which return for me that set:</p>
  
  <pre><code>- (void)allDialogsWithPageLimit:(NSUInteger)limit
                  extendedRequest:(QB_NULLABLE NSDictionary *)extendedRequest
                   iterationBlock:(void(^QB_NULLABLE_S )(QBResponse *QB_NONNULL_S response, NSArray QB_GENERIC(QBChatDialog *) *QB_NULLABLE_S dialogObjects, NSSet QB_GENERIC(NSNumber *) * QB_NULLABLE_S dialogsUsersIDs, BOOL * QB_NONNULL_S stop))iterationBlock
                       completion:(void(^QB_NULLABLE_S)(QBResponse * QB_NONNULL_S response))completion;
  </code></pre>
  
  <p>As you see we got that NSSet from here:</p>
  
  <pre><code>NSSet QB_GENERIC(NSNumber *) * QB_NULLABLE_S dialogsUsersIDs
  </code></pre>
  
  <p>that method is from <a href="https://github.com/QuickBlox/q-municate-services-ios/blob/c32eddd73cc3b5cc3481610ff0f04b6fbade97e8/QMChatService/QMChatService/QMChatService.h" rel="nofollow">QuickBlox SDK</a></p>