plugin-loader: don't critical if a plugin lazily implements no sidecars
plugin-loader: don't critical if a plugin lazily implements no sidecars

An empty strv is really { NULL }, but it's not so unreasonable to
use just NULL instead, so we shouldn't break if we get that.

Creating a sidecar is safe as it checks whether the strv contains the
requested interface using tp_strv_contains() which treats NULL as an
empty strv.

Signed-off-by: Jonny Lamb <3d1fb3642aaab2ff70e3392a5ab916bf99eed6a3@collabora.co.uk>

freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut,freedesktop-unofficial-mirror/telepathy__telepathy-salut