[controller] FSAjaxController: check for existance in filelist

vispa/controller/filesystem.py

@@ -154,6 +154,9 @@ class FSAjaxController(AbstractController):
         reverse = self.convert(reverse, bool)
         hide_hidden = self.convert(hide_hidden, bool)
 
+        if not fs.exists(path):
+            raise AjaxException("there is no such file: %s" % path)
+
         # get the files with the filter
         return fs.get_file_list(path, filter=filefilter,
                                 reverse=reverse, encode_json=True,