Dynamically expand index_cache if too small

Re-application of 502b6a82a3

jmclient/jmclient/wallet.py

@@ -183,6 +183,13 @@ class Wallet(AbstractWallet):
                 walletdata['network'], get_network()))
         if 'index_cache' in walletdata:
             self.index_cache = walletdata['index_cache']
+            if self.max_mix_depth > len(self.index_cache):
+                #This can happen e.g. in tumbler when we need more mixdepths
+                #than currently exist. Since we have no info for those extra
+                #depths, we must default to (0,0) (but sync should find used
+                #adddresses).
+                self.index_cache += [[0,0]] * (
+                    self.max_mix_depth - len(self.index_cache))
         password_key = btc.bin_dbl_sha256(pwd)
         encrypted_seed = walletdata['encrypted_seed']
         try: