[PATCH] drm/radeon: Fix potential null-ptr-deref

Due to my rookie mistake this patch isn't necessary anymore in upstream version. The issue was already resolved in a different manner. Apologies for inconvenience.

[PATCH] drm/radeon: Fix potential null-ptr-deref

radeon_get_connector_for_encoder() assigns radeon_encoder->enc_priv to mst_enc which is dereferenced later without being checked for NULL beforehand. It is possible for radeon_encoder->enc_priv and therefore mst_enc, to be NULL due to potential lack of memory. This patch adds a sanity NULL-check t