Index: /CKEditor/trunk/_source/plugins/colorbutton/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/colorbutton/plugin.js	(revision 6291)
+++ /CKEditor/trunk/_source/plugins/colorbutton/plugin.js	(revision 6292)
@@ -74,5 +74,5 @@
 							color = block && block.getComputedStyle( type == 'back' ? 'background-color' : 'color' ) || 'transparent';
 						}
-						while ( type == 'back' && color == 'transparent' && ( block = block.getParent() ) );
+						while ( type == 'back' && color == 'transparent' && block && ( block = block.getParent() ) );
 
 						// The box should never be transparent.