fix(lib): type errors

libs/ui/src/lib/toggle/toggle.component.ts

@@ -26,13 +26,17 @@ export class GfToggleComponent implements OnChanges {
 
   @Output() valueChange = new EventEmitter<Pick<ToggleOption, 'value'>>();
 
-  public optionFormControl = new FormControl<string>(undefined);
+  public optionFormControl = new FormControl<string | null>(null);
 
   public ngOnChanges() {
     this.optionFormControl.setValue(this.defaultValue);
   }
 
   public onValueChange() {
-    this.valueChange.emit({ value: this.optionFormControl.value });
+    const value = this.optionFormControl.value;
+
+    if (value !== null) {
+      this.valueChange.emit({ value });
+    }
   }
 }