--- a/DiffTextView.st	Tue Apr 26 15:20:38 2016 +0200
+++ b/DiffTextView.st	Wed Apr 27 12:26:01 2016 +0200
@@ -600,7 +600,8 @@
 
     |container vScroller thumb|
 
-    (container := self container) isScrollWrapper ifTrue:[
+    ((container := self container) notNil
+    and:[container isScrollWrapper]) ifTrue:[
         (vScroller := container verticalScrollBar) notNil ifTrue:[
             (thumb := vScroller thumb) notNil ifTrue:[
                 thumb viewBackground:(DiffTextScrollerBackground new diffView:self).