Why is there a “File not found” image on my post?

The ubiquitous File not found image, explained:

This image will appear when IFTTT is set up to post an image or a file, but we don't get the data as expected.

Here's an example to illustrate further. The Applet below is configured to tweet with an image each time your Tumblr has a new post. Since the Applet is expecting an image with the tweet, Tumblr posts without an image will fall back to the File not found image above. 

If you're seeing this error message often, we recommend using an action that is not expecting an image each time it runs. Actions that are expecting images will contain an Image URL ingredient.

How to avoid the File not found image with filter code

You can skip an Applet's action when the 'File not found' image is set to be used with the following filter code:

let imageURL = Tumblr.newAnyPost.PostImageUrl;
let noImage = 'no_image_card.png';

if ( imageURL.indexOf(noImage) !== -1 ) {  
   Twitter.postNewTweetWithImage.skip();
}

Note that this code is specific to the Tumblr > Twitter Applet mentioned above. If you'd like to use this filter code in your Applet, Tumblr.newAnyPost.PostImageUrl and Twitter.postNewTweetWithImage.skip() will need to be replaced with your trigger's ImageURL ingredient and your action's skip code, respectively.