Fix image cropper not closing correctly

Originally it gives the following error:

Uncaught (in promise) TypeError: e.destroy is not a function
    submit image_cropper.js:80
    promise callback*submit image_cropper.js:80
    1 image_cropper.vue:17
    s runtime-core.esm-bundler.js:155
    u runtime-core.esm-bundler.js:164
    n runtime-dom.esm-bundler.js:373
    y runtime-dom.esm-bundler.js:316
    _ runtime-dom.esm-bundler.js:334

src/components/image_cropper/image_cropper.js

@@ -66,7 +66,7 @@ const ImageCropper = {
     }
   },
   methods: {
-    unmounted () {
+    destroy () {
       if (this.cropper) {
         this.cropper.destroy()
       }