fix: do not create old_wallet if seed is empty because user typed gibberish

lib/wallet.py

@@ -1717,6 +1717,10 @@ class OldWallet(Wallet):
 
         self.seed = mnemonic.mn_decode(words)
 
+        if not self.seed:
+            raise Exception("Invalid seed")
+            
+
 
     def get_master_public_key(self):
         return self.storage.get("master_public_key")