fix Swift 5.0 build

Sources/CryptoSwift/Cryptors.swift

@@ -37,6 +37,6 @@ extension Cryptors {
   /// Convenience helper that uses `Swift.RandomNumberGenerator`.
   /// - Parameter count: Length of array
     public static func randomIV(_ count: Int) -> Array<UInt8> {
-      (0..<count).map({ _ in UInt8.random(in: 0...UInt8.max) })
+      return (0..<count).map({ _ in UInt8.random(in: 0...UInt8.max) })
     }
 }