Noissue - Fix *_BINARY=installed after update to selenium-webdriver 4.0

test/all.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 11 matching lines @@
 const {exec} = require("child_process");
 
 function getBrowserBinary(module, browser)
 {
   let spec = process.env[`${browser.toUpperCase()}_BINARY`];
   let version = module.oldestCompatibleVersion;
 
   if (spec)
   {
     if (spec == "installed")
-      return Promise.resolve("");
+      return Promise.resolve(null);
     if (spec.startswith("path:"))
       return Promise.resolve(spec.substr(5));
     if (spec.startsWith("download:"))
       version = spec.substr(9);
   }
 
   return module.ensureBrowser(version);
 }
 
 for (let browser of glob.sync("./test/browsers/*.js"))
@@ skipping 50 matching lines @@
       require(modulePath);
     }
 
     after(function()
     {
       if (this.driver)
         return this.driver.quit();
     });
   });
 }