[FIX] base_import: prevent trackback while upload unidentified image URL

 This issue occurs when a customer imports or uploads a file, and that file
 contains an image that is attached to the URL as text or HTML. then,
 The error would be generated.

  Step to Produce:-
 - import CSV file (Ex.'product.product' model)
    > that CSV file must have one URL Image(In that URL has content of text or
      Html form)
 - Click On the 'Test' Button.

  Applying these changes will resolve this issue.

  sentry:-4046190590

closes odoo/odoo#119499

Signed-off-by: Achraf Ben Azzouz (abz) <abz@odoo.com>