glTF: More rendering related error handling

If any error occurs related to glTF rendering, a question
mark is displayed at the place of the OpenGL window
(Question mark is a general concept of media objects).

Change-Id: Id7df5a47a4dd6832e640b3a7cb3c7712ebfb4408
(cherry picked from commit 58fd5a6dd6d5d599df88c9fd4ed5257577562bd9)
Reviewed-on: https://gerrit.libreoffice.org/10275
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>