fix: sanitize outputs

lib/paymentrequest.py

@@ -57,9 +57,6 @@ class PaymentRequest:
         self.outputs = []
         self.error = ""
 
-    def get_amount(self):
-        return sum(map(lambda x:x[1], self.outputs))
-
 
     def verify(self):
         u = urlparse.urlparse(self.url)

lib/wallet.py

@@ -118,7 +118,7 @@ class WalletStorage:
         with self.lock:
             if value is not None:
                 self.data[key] = value
-            else:
+            elif key in self.data:
                 self.data.pop(key)
             if save: 
                 self.write()