handle network.interface being None when network is disconnected

lib/blockchain.py

@@ -92,7 +92,11 @@ class Blockchain(threading.Thread):
                     print_error("error", i.server)
                     # todo: dismiss that server
 
-            h = self.servers_height.get(self.network.interface.server)
+            if self.network.is_connected():
+                h = self.servers_height.get(self.network.interface.server)
+            else:
+                h = None
+
             if h is not None and h < height - 1:
                 print_error( "Server is lagging", height, h)
                 if self.config.get('auto_cycle'):

lib/network.py

@@ -166,6 +166,11 @@ class Network(threading.Thread):
             return self.interface.is_connected
 
 
+    def wait_until_connected(self):
+        while not self.interface:
+            time.sleep(1)
+        self.interface.connect_event.wait()
+
     def set_proxy(self, proxy):
         self.proxy = proxy
 
@@ -175,7 +180,9 @@ class Network(threading.Thread):
             return
 
         # stop the interface in order to terminate subscriptions
-        self.interface.stop() 
+        if self.interface:
+            self.interface.stop() 
+
         # notify gui
         self.trigger_callback('disconnecting')
         # start interface

lib/wallet.py

@@ -1510,12 +1510,12 @@ class WalletSynchronizer(threading.Thread):
             self.running = True
 
         while self.is_running():
-            interface = self.network.interface
-            if not interface.is_connected:
+            
+            if not self.network.is_connected():
                 print_error("synchronizer: waiting for interface")
-                interface.connect_event.wait()
+                self.network.wait_until_connected()
                 
-            self.run_interface(interface)
+            self.run_interface(self.network.interface)
 
 
     def run_interface(self, interface):