Don't call v4l2_ctrl_g_ctrl on ctrls which the model cam in question
does not have.
Reported-by: NFrank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
[ Taken directly, since Mauro is on vacation ]
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>