Fix code warning (#2)

Author: svlaev

iOSDropDown/Classes/iOSDropDown.swift

@@ -224,11 +224,10 @@ open class DropDown : UITextField{
         table.backgroundColor = rowBackgroundColor
         table.rowHeight = rowHeight
         if scrollToSelectedIndex{
-            if selectedIndex != nil{
-                if let indexPath = NSIndexPath(row: selectedIndex!, section: 0) as? IndexPath{
-                    self.table.scrollToRow(at: indexPath, at: .top, animated: true)
-                    self.table.reloadData()
-                }
+            if let selectedIndex = selectedIndex {
+                let indexPath = IndexPath(row: selectedIndex, section: 0)
+                self.table.scrollToRow(at: indexPath, at: .top, animated: true)
+                self.table.reloadData()
             }
         }
         parentController?.view.addSubview(shadow)