The return statement is missing altogether and an error is silently
ignored. Fix this and also update the empty map to use the correct type
for the map key.
Fixes: 65ea2422d2 ("libcamera: camera: extend camera object to support configuration of streams")
Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>