.tiff files cause error on refresh

[karmatosed]

To reproduce:

• Click image block
• Add a .tiff file
• Nothing shows
• Refresh
• This shows:

[aduth]

Uncaught TypeError: Cannot convert undefined or null to object

The issue is that we expect the media item to return a media_details.sizes object on the API return value:

gutenberg/blocks/library/image/block.js

Lines 81 to 85 in fdb1158

	this.fetchImageRequest.then( ( image ) => {
	this.setState( {
	availableSizes: image.media_details.sizes,
	} );
	} );

In the case of a TIFF image, the media_details property is an empty object, so availableSizes state is assigned as undefined.

[karmatosed]

@aduth can we do something to catch this for .tiff?