Fix crash

SignalServiceKit/src/Loki/API/LokiSnodeProxy.swift

@@ -79,7 +79,7 @@ internal class LokiSnodeProxy : LokiHTTPClient {
             task.resume()
             return promise
         }.map { rawResponse in
-            guard let data = rawResponse as? Data, let cipherText = Data(base64Encoded: data) else {
+            guard let data = rawResponse as? Data, !data.isEmpty, let cipherText = Data(base64Encoded: data) else {
                 print("[Loki] Received a non-string encoded response.")
                 return rawResponse
             }

SignalServiceKit/src/Loki/Crypto/DiffieHellman.swift

@@ -24,6 +24,7 @@ public enum DiffieHellman {
     
     public static func decrypt(_ encryptedData: Data, using symmetricKey: Data) throws -> Data {
         let symmetricKeyBytes = [UInt8](symmetricKey)
+        guard encryptedData.count >= ivLength else { throw "Couldn't decrypt data." }
         let ivBytes = [UInt8](encryptedData[..<ivLength])
         let cipherBytes = [UInt8](encryptedData[ivLength...])
         let blockMode = CBC(iv: ivBytes)