Update browser.js

source/browser.js

@@ -31,7 +31,7 @@ browser.Host = class {
             repository: this._element('logo-github').getAttribute('href'),
             menu: true
         };
-        if (!/^\d\.\d\.\d$/.test(this.version)) {
+        if (this.version && !/^\d\.\d\.\d$/.test(this.version)) {
             throw new Error('Invalid version.');
         }
     }