[pitivi] guidelines: Fix drawing

[Alexandru Băluț <alexbalut src gnome org>]

commit ba3566bf4a6ae8bfeba9974f3d32ad45f1986faa
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Fri May 8 21:58:55 2020 +0200

    guidelines: Fix drawing

 pitivi/viewer/guidelines.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/pitivi/viewer/guidelines.py b/pitivi/viewer/guidelines.py
index d6fd6b7f..f5dcefd3 100644
--- a/pitivi/viewer/guidelines.py
+++ b/pitivi/viewer/guidelines.py
@@ -55,7 +55,7 @@ class Guideline(Enum):
 
     def __init__(self, label, func):
         self.label = label
-        self.draw_func = func
+        self.draw_func = func.__func__
 
 
 class GuidelinesPopover(Gtk.Popover):