Check for a valid image file when uploading logo

[aydwi]

Bug

Description

In the journalist application, when the Admin uploads an image file for logo, no check is performed to determine if it is a valid image file, or a corrupted/unreadable one. The application currently only checks for a valid extension.

Thus if someone uploads a corrupt/unreadable or non-image file with an extension like JPG, JPEG or PNG, it gets updated and shows up like:

Steps to Reproduce

Upload a non-image file with .png extension.

Expected Behavior

The image should be ignored and user should be prompted to upload again.

Actual Behavior

The incorrect image file gets uploaded.

Comments

As suggested by @heartsucker, I'll try to write a fix for this and integrate into #3057