How to solve the problem that changing the face value of the picture causes the upload button of ng2-file-upload to be invalid?

<select class="input-group-sm form-control">
    <option>{{xx}}</option>
</select>

<input -sharpfileSelect type="file" ng2FileSelect [uploader]="uploader" (change)="bb($event)" />

<button class="btn-font-size btn btn-primary btn-block" (click)="aaa()" [disabled]="!uploader.getNotUploadedItems().length">
   <span class="glyphicon glyphicon-upload"></span>Upload
</button>

situation restore:
I first select a file, then click select to select a value, and find that upload button is invalid.
is there a great god who can help?

Typescript angular2

Mar.02,2021

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