drm: Handle drm_object_get() failures

Check drm_mode_object_get() return value everywhere.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index d761d12..d9d6684 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -352,6 +352,8 @@
 		return true;
 
 	adjusted_mode = drm_mode_duplicate(dev, mode);
+	if (!adjusted_mode)
+		return false;
 
 	saved_hwmode = crtc->hwmode;
 	saved_mode = crtc->mode;