Fix checking of window global variable in strict mode

Previous version of the check failed in strict mode with error
"window is not defined". Strict mode is default in Webpack.

src/v1/internal/browser/browser-channel.js

@@ -300,5 +300,5 @@ function verifyEncryptionSettings(encryptionOn, encryptionOff, secureProtocol) {
 }
 
 function detectWebPageProtocol() {
-  return window && window.location ? window.location.protocol : null;
+  return typeof window != 'undefined' && window.location ? window.location.protocol : null;
 }