The issue of uploading the same image consecutively.

**To Reproduce**
Set the imageUploadFunction parameter
When uploading the same image consecutively, the first attempt succeeds, but there is no response for subsequent attempts. If a different image is uploaded, it succeeds again.

```
var easyMDE = new EasyMDE({
element: editor[0],
promptURLs: true,
forceSync: true,
toolbar: [
"bold", "strikethrough", "italic", "heading", "heading-2", "heading-3", "|",
"code", "quote", "|",
"unordered-list", "ordered-list", "table", "|",
"link", "upload-image", "|", "preview", "side-by-side", "fullscreen", "|",
"guide"
],
uploadImage: true,
status: false,
imageUploadFunction: (file, onSuccess, onError) => {
alert(444);
}
});
```
Uploading the same image, the above code will only pop up 444 once.