Sometimes cloudinary fails to generate thumbnails

[jmaupetit]

Purpose

The following urls generates a 400 error:

1. https://res.cloudinary.com/tailordev/image/fetch/c_thumb,w_370,h_200,f_png/https://ndownloader.figshare.com/files/2080690
2. https://res.cloudinary.com/tailordev/image/fetch/c_thumb,w_370,h_200,f_png/https://ndownloader.figshare.com/files/2094771

The consequence is that no thumbnail is generated for this poster in the mobile app.

Failure reasons may be:

• File size too large. Got 16982431. Maximum is 10485760 (case 1)
• Invalid resource (case 2)

Proposal

As suggested by @willdurand, we need a placeholder in those cases.