fix #3964

lib/util.py

@@ -419,6 +419,8 @@ def format_satoshis(x, is_diff=False, num_zeros = 0, decimal_point = 8, whitespa
     return result
 
 def timestamp_to_datetime(timestamp):
+    if timestamp is None:
+        return None
     return datetime.fromtimestamp(timestamp)
 
 def format_time(timestamp):

lib/wallet.py

@@ -1000,7 +1000,7 @@ class Abstract_Wallet(PrintError):
                 'value': Satoshis(value),
                 'balance': Satoshis(balance)
             }
-            item['date'] = timestamp_to_datetime(timestamp) if timestamp is not None else None
+            item['date'] = timestamp_to_datetime(timestamp)
             item['label'] = self.get_label(tx_hash)
             if show_addresses:
                 tx = self.transactions.get(tx_hash)