Fix check for an empty input or ESC key press

According to the task both of these should give an alert('Canceled'). Previous solution implied that both empty input and ESC key return null, but in Chrome 64.0.3282.186 an empty input returns '' instead of null. So we are adding an additional check.

Author: snakecase

1-js/02-first-steps/10-ifelse/4-check-login/solution.md

@@ -9,13 +9,13 @@ if (userName == 'Admin') {
 
   if (pass == 'TheMaster') {
     alert( 'Welcome!' );
-  } else if (pass == null) {
+  } else if (pass == '' || pass == null) {
     alert( 'Canceled.' );
   } else {
     alert( 'Wrong password' );
   }
 
-} else if (userName == null) {
+} else if (userName == '' || userName == null) {
   alert( 'Canceled' );
 } else {
   alert( "I don't know you" );