only set watch on attrs.layoutDisabled when attribute is defined

services/web/public/coffee/ide/directives/layout.coffee

@@ -103,12 +103,12 @@ define [
 
 					resetOpenStates()
 					onInternalResize()
-					
-					scope.$watch attrs.layoutDisabled, (value) ->
-						if value
-							element.layout().hide("east")
-						else
-							element.layout().show("east")
-							
+
+					if attrs.layoutDisabled?
+						scope.$watch attrs.layoutDisabled, (value) ->
+							if value
+								element.layout().hide("east")
+							else
+								element.layout().show("east")
 		}
-	]
+	]