An error for the missing image is thrown:
GET https://localhost:63252/test.png 404 (Not Found)
No error is thrown, since the value of the background-image property has been replaced with "none" in the Editor events and the actual content the Editor visualizes does not use the image:
<tr style="box-sizing: border-box; border-style: solid; border-width: 1px 0px; background-image: none;">
...
</tr>