fix a crash happening when long mnemonic is used to recover an account

Session/Onboarding/RestoreVC.swift

@@ -198,7 +198,7 @@ final class RestoreVC: BaseVC {
         do {
             let hexEncodedSeed = try Mnemonic.decode(mnemonic: mnemonic)
             let seed = Data(hex: hexEncodedSeed)
-            let (ed25519KeyPair, x25519KeyPair) = try! Identity.generate(from: seed)
+            let (ed25519KeyPair, x25519KeyPair) = try Identity.generate(from: seed)
             Onboarding.Flow.recover.preregister(with: seed, ed25519KeyPair: ed25519KeyPair, x25519KeyPair: x25519KeyPair)
             mnemonicTextView.resignFirstResponder()
             

SessionUtilitiesKit/Database/Models/Identity.swift

@@ -53,7 +53,7 @@ extension ECKeyPair {
 
 public extension Identity {
     static func generate(from seed: Data) throws -> (ed25519KeyPair: Sign.KeyPair, x25519KeyPair: ECKeyPair) {
-        assert(seed.count == 16)
+        guard (seed.count == 16) else { throw GeneralError.invalidSeed }
         let padding = Data(repeating: 0, count: 16)
         
         guard

SessionUtilitiesKit/General/General.swift

@@ -19,6 +19,7 @@ public enum General {
 }
 
 public enum GeneralError: Error {
+    case invalidSeed
     case keyGenerationFailed
 }