chat-dialog: fix gui bug when changing routing prefix

Change-Id: I7029856fe1a3f1c40f2650008a7ceb6ad2b9dfec
Refs: #2484
diff --git a/src/chat-dialog-backend.cpp b/src/chat-dialog-backend.cpp
index 1ea25ac..354b9bd 100644
--- a/src/chat-dialog-backend.cpp
+++ b/src/chat-dialog-backend.cpp
@@ -485,14 +485,14 @@
     // Update localPrefix
     m_localRoutingPrefix = newLocalRoutingPrefix;
 
-    updatePrefixes();
-
     m_mutex.lock();
     m_shouldResume = true;
     m_mutex.unlock();
 
     close();
 
+    updatePrefixes();
+
     m_face->getIoService().stop();
   }
 }