From 51ed8a998c0f80fe27a3c27c46e4ff12d875865b Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Mon, 25 Jun 2018 01:14:49 +0200
Subject: [PATCH] fix: network.interface can become None at any time

---
 gui/kivy/main_window.py  | 5 +++--
 gui/qt/network_dialog.py | 3 ++-
 lib/synchronizer.py      | 4 +++-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/gui/kivy/main_window.py b/gui/kivy/main_window.py
index 11eced5f7..0291bdd0a 100644
--- a/gui/kivy/main_window.py
+++ b/gui/kivy/main_window.py
@@ -639,8 +639,9 @@ class ElectrumWindow(App):
         chain = self.network.blockchain()
         self.blockchain_checkpoint = chain.get_checkpoint()
         self.blockchain_name = chain.get_name()
-        if self.network.interface:
-            self.server_host = self.network.interface.host
+        interface = self.network.interface
+        if interface:
+            self.server_host = interface.host
 
     def on_network_event(self, event, *args):
         Logger.info('network event: '+ event)
diff --git a/gui/qt/network_dialog.py b/gui/qt/network_dialog.py
index e578bb43a..f9a1f7da7 100644
--- a/gui/qt/network_dialog.py
+++ b/gui/qt/network_dialog.py
@@ -340,7 +340,8 @@ class NetworkChoiceLayout(object):
         self.server_port.setText(port)
         self.autoconnect_cb.setChecked(auto_connect)
 
-        host = self.network.interface.host if self.network.interface else _('None')
+        interface = self.network.interface
+        host = interface.host if interface else _('None')
         self.server_label.setText(host)
 
         self.set_protocol(protocol)
diff --git a/lib/synchronizer.py b/lib/synchronizer.py
index b792bd4d3..3a8dc0bba 100644
--- a/lib/synchronizer.py
+++ b/lib/synchronizer.py
@@ -126,7 +126,9 @@ class Synchronizer(ThreadJob):
         tx_fees = dict(filter(lambda x:x[1] is not None, tx_fees))
         # Note if the server hasn't been patched to sort the items properly
         if hist != sorted(hist, key=lambda x:x[1]):
-            self.network.interface.print_error("serving improperly sorted address histories")
+            interface = self.network.interface
+            # note: we don't actually know which interface was used if it was *just* changed
+            if interface: interface.print_error("serving improperly sorted address histories")
         # Check that txids are unique
         if len(hashes) != len(result):
             self.print_error("error: server history has non-unique txids: %s"% addr)