🩹 Fix wrong tag index in TagsInput when updated via python (#3862)

Author: s-weigand

Diff for: packages/controls/src/widget_tagsinput.ts

@@ -167,6 +167,7 @@ abstract class TagsInputBaseView extends DOMWidgetView {
     this.tags = [];
 
     const value: Array<any> = this.model.get('value');
+    this.inputIndex = value.length;
     for (const idx in value) {
       const index = parseInt(idx);