Fix slight bug in context error handler

lib/context.js

@@ -106,7 +106,7 @@ const proto = module.exports = {
     // don't do anything if there is no error.
     // this allows you to pass `this.onerror`
     // to node-style callbacks.
-    if (null == err) return;
+    if (!err) return;
 
     if (!(err instanceof Error)) err = new Error(util.format('non-error thrown: %j', err));
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "koa-lite",
-  "version": "2.10.0",
+  "version": "2.10.1",
   "description": "Lite version of the Koa web app framework",
   "main": "lib/application.js",
   "scripts": {