In case we couldn't enable the output do not return early without
setting the proper return value. This causes an issue later one, because
the signal list isn't initalized, taking down the compositor with a crash.
Bug-AGL: SPEC-4734 Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: Ia5ebc226f6b8f702e710a5976c471d04302bcb00