fix(plugin): root should not be empty

Author: azu

src/plugin.js

@@ -52,7 +52,7 @@ window.require(["gitbook"], function(gitbook) {
         reportElement.setAttribute("style", "position:fixed; right:0;bottom:0;");
         var clickEvent = ("ontouchstart" in window) ? "touchend" : "click";
         reportElement.addEventListener(clickEvent, function(event) {
-            var pathname = path.join(gitbook.state.config.root, gitbook.state.filepath);
+            var pathname = path.join(gitbook.state.config.root || "./", gitbook.state.filepath);
             var apiURL = getAPIURL(config, pathname);
             var resourceURL = getResourceURL(config, pathname, "master");
             var editURL = getEditURL(config, pathname, "master");