TermInput.js : Fix unwanted space in input field

After adding a term by pressing the spacebar, an unwanted space was inserted into the input field.
This happens because the if condition was always false, since we cannot read the length from the
object with the .length property.

asset/js/widget/TermInput.js

@@ -88,7 +88,7 @@ define(["BaseInput"], function (BaseInput) {
             }
 
             let addedTerms = this.exchangeTerm();
-            if (addedTerms.length) {
+            if (Object.keys(addedTerms).length) {
                 this.togglePlaceholder();
                 event.preventDefault();
                 this.autoSubmit(this.input, 'exchange', addedTerms);