Fix error handling issue

LokiKit/LokiKit/ECKeyPair.h

@@ -2,6 +2,7 @@
 
 @interface ECKeyPair (ECKeyPairExtension)
 
+/// Based on `ECKeyPair.generateKeyPair()`.
 + (nonnull ECKeyPair *)generateKeyPairWithHexEncodedPrivateKey:(nonnull NSString *)hexEncodedPrivateKey;
 
 @end

LokiKit/LokiKit/Mnemonic/Mnemonic.swift

@@ -47,7 +47,7 @@ public enum Mnemonic {
     public enum DecodingError : LocalizedError {
         case generic, inputTooShort, missingLastWord, invalidWord, verificationFailed
         
-        public var errorDescription: String {
+        public var errorDescription: String? {
             switch self {
             case .generic: return NSLocalizedString("Something went wrong. Please check your mnemonic and try again.", comment: "")
             case .inputTooShort: return NSLocalizedString("Looks like you didn't enter enough words. Please check your mnemonic and try again.", comment: "")

Signal/src/ViewControllers/Registration/OnboardingKeyPairViewController.swift

@@ -207,7 +207,6 @@ final class OnboardingKeyPairViewController : OnboardingBaseViewController {
             } catch let error {
                 let error = error as? Mnemonic.DecodingError ?? Mnemonic.DecodingError.generic
                 errorLabel.text = error.errorDescription
-                errorLabel.isHidden = false
                 return
             }
         }