[FIX] web: clear filename if image error

When the user chooses as product image a file which is not an image, the
message "Could not display the selected image" is displayed. However, at
saving, a traceback is thrown since the file chosen is uploaded anyway.

If the image cannot be displayed, the image field is cleared.

opw-672206

addons/web/static/src/js/views/form_widgets.js

@@ -1362,6 +1362,7 @@ var FieldBinaryImage = FieldBinary.extend({
             $img.css("max-height", "" + self.options.size[1] + "px");
         });
         $img.on('error', function() {
+            self.on_clear();
             $img.attr('src', self.placeholder);
             self.do_warn(_t("Image"), _t("Could not display the selected image."));
         });