Empty action sets field value to "undefined"

Actually the first patch doesn't work, it doesn't empty the fields. I trying this

diff --git a/js/conditional_fields.js b/js/conditional_fields.js
index 61e0bbd..b73d9be 100644
--- a/js/conditional_fields.js
+++ b/js/conditional_fields.js
@@ -70,6 +70,9 @@
           if (e.effect) {
             if (e.value) {
               this.value = e.effect.value;
+              if (typeof e.effect.value === 'undefined') {
+                this.value = '';
+              }
             } else if ($(this).data('conditionalFieldsSavedValue')) {
               this.value = $(this).data('conditionalFieldsSavedValue');
             }

Probably a better/different way to solve this maybe module maintainers know.

The reason why we have this issue:

4.0.0-alpha5
$(this).val(e.effect.value);
val(undefined) in jQuery sets the value to an empty string (""), not string "undefined".

4.0.0-alpha6
this.value = e.effect.value;
e.effect.value is undefined, the value property is set to string "undefined"

Diff from previous patch:

• replaced if with nullish coalescing operator
• added some comments.