Wrap another call of collect_windows().

diff --git a/qwerty.py b/qwerty.py
index a2e2401..d811296 100755
--- a/qwerty.py
+++ b/qwerty.py
@@ -675,7 +675,11 @@ class GUI(object):
         self.window.show_all()
         self.taskbar.hide()

-        self.collect_windows()
+        try:
+            self.collect_windows()
+        except:
+            self.clients_list = []
+            print 'Could not get list of open windows!'

     def calc_sizes(self):
         global LABEL_FONT_SIZE
@@ -934,6 +938,7 @@ class GUI(object):
         try:
             self.collect_windows()
         except:
+            self.clients_list = []
             print 'Could not get list of open windows!'

         id = (int(k)-1)%10