null check error in pdf view

services/web/public/coffee/ide/pdfng/directives/pdfViewer.coffee

@@ -369,7 +369,7 @@ define [
 				scope.$on 'pdf:error', (event, error) ->
 					return if error == 'cancelled'
 					# check if too many retries or file is missing
-					if scope.loadCount > 3 || error.match(/^Missing PDF/i) || error.match(/^loading/i)
+					if scope.loadCount > 3 || error?.match(/^Missing PDF/i) || error?.match(/^loading/i)
 						scope.$emit 'pdf:error:display'
 						return
 					if scope.loadSuccess