thumbnail: do not try resizing missing files

panikweb/paniktags/templatetags/thumbnails.py

@@ -28,7 +28,7 @@ def thumbnail(image, size='100x100'):
             os.path.getmtime(filename) > os.path.getmtime(miniature_filename):
         os.unlink(miniature_filename)
     # if the image wasn't already resized, resize it
-    if not os.path.exists(miniature_filename):
+    if not os.path.exists(miniature_filename) and os.path.exists(filename):
         image = Image.open(filename)
         if abs( (1.0*x/y) - (1.0*image.size[0]/image.size[1]) ) > 0.1:
             # aspect ratio change, crop the image first