Wrap collect_windows() call to try..excet. Some WMs do not set

diff --git a/qwerty.py b/qwerty.py
index c4db872..a2e2401 100755
--- a/qwerty.py
+++ b/qwerty.py
@@ -41,7 +41,7 @@ LINEHEIGHT = 1.2
 KEYS = [ "QWERTYUIOP",
          "ASDFGHJKL",
          "ZXCVBNM" ]
-ALPHABET = KEYS[0] + KEYS[1] + KEYS[2]
+ALPHABET = ''.join(KEYS)

 DIGITS = '1234567890'

@@ -931,7 +931,10 @@ class GUI(object):
         if not mods:
             mods = []

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

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