backends/drm: Create DrmPipeline regardless whether drmModeGetConnector() succeeds
If the drmModeGetConnector() in the DrmConnector constructor fails but one in the updateProperties() does not, the connector can be still used.
In which case, kwin is going to crash later because the DrmPipeline is null (since the initial drmModeGetConnector() failed).
Since the DrmPipeline doesn't need any drmModeConnector properties, it can be created regardless of whether the connector is probed successfully.
More problems are still expected though because m_possibleCrtcs is not initialized properly, but at least, kwin will not crash.
SENTRY: KWIN-8J5