fix: do not request the same history twice

lib/wallet.py

@@ -1252,6 +1252,7 @@ class WalletSynchronizer(threading.Thread):
             if method == 'blockchain.address.subscribe':
                 addr = params[0]
                 if self.wallet.get_status(self.wallet.get_history(addr)) != result:
+                    if requested_histories.get(addr) is None:
                         self.interface.send([('blockchain.address.get_history', [addr])], 'synchronizer')
                         requested_histories[addr] = result