Fix value, value highlighting in editor

src/app/list-field/list-field.component.ts

@@ -28,6 +28,7 @@ import { ProtoFieldComponent } from '../proto-field/proto-field.component';
       <app-proto-field
         [configuration]="configuration().subConfiguration"
         [value]="value"
+        (valueChange)="updateValue($index, $event)"
       ></app-proto-field>
       <button mat-icon-button (click)="remove($index)">
         <mat-icon>remove</mat-icon>
@@ -44,18 +45,25 @@ export class ListFieldComponent {
   values = model<any[]>();
 
   add() {
-    const newValues = this.values();
-    if (newValues) {
-      newValues.push(null);
+    const existingValues = this.values();
+    if (existingValues) {
+      const newValues = [...existingValues];
+      newValues.push(undefined);
       this.values.set(newValues);
     } else {
-      this.values.set([null]);
+      this.values.set([undefined]);
     }
   }
 
   remove(index: number) {
-    const newValues = this.values();
-    newValues?.splice(index, 1);
+    const newValues = [...this.values()!];
+    newValues.splice(index, 1);
     this.values.set(newValues);
   }
+
+  updateValue(index: number, value: any) {
+    let existing = [...this.values()!];
+    existing[index] = value;
+    this.values.set(existing);
+  }
 }