Ensure Application.update_status() is passed an Engine

AttributeError: 'QThread' object has no attribute 'uid'
  File "nxdrive\gui\application.py", line 1220, in update_status

diff --git a/nxdrive/gui/application.py b/nxdrive/gui/application.py
index f358a036..ad308eb0 100644
--- a/nxdrive/gui/application.py
+++ b/nxdrive/gui/application.py
@@ -1258,8 +1258,11 @@ class Application(QApplication):
         """
         sync_state = error_state = update_state = ""
 
+        if not isinstance(engine, Engine):
+            log.error(f"Need an Engine, got {engine!r}")
+            return
+
         update_state = self.manager.updater.status
-        self.refresh_conflicts(engine.uid)
 
         # Check synchronization state
         if self.manager.restart_needed: