Display more user-friendly error when uploading non-picture file as a picture

[AndreiMaz]

Steps to reproduce the problem:

1. Upload any non-picture file (e.g. XML or .cs) as a picture. For example, on a product details page
2. It gives a correct message that uploading failed. But also, 'Object reference not set to an instance of an object.' throwing error on picture controller side.

Let's handle the exception so it's not thrown. There should be just an error text without an unhandled exception

Source: https://www.nopcommerce.com/en/boards/topic/84221/picture-controller-in-get-error-object-reference-not-set-to-an-instance-of-an-object

[badijm]

Hi, I can grab this item if available.

[badijm]

@AndreiMaz Hi, I've send the PR. Lemme know if it works for ya.

[AndreiMaz]

@badijm Please create the PR at https://github.com/nopSolutions/nopCommerce/pulls and share the link here

[badijm]

@AndreiMaz #4963

[holydk]

Closed #4919