I get an error with use flat

[doox911]

<upload-btn flat class="pa-0 primary--text" noTitleUpdate title="Выбрать excel файл" @file-update="exportFile" ref="upload_file_button" > </upload-btn>

[Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "color"

And do not work :loading="loading"