drm/amd/display: add null checks before logging

Adding NULL checks to various parameters in log_tf, to avoid
nullptr errors
Signed-off-by: Wyatt Wood <wyatt.wood@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Acked-by: Nikola Cornij <Nikola.Cornij@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c

@@ -1503,9 +1503,12 @@ dcn10_set_output_transfer_func(struct pipe_ctx *pipe_ctx,
 	} else
 		dpp->funcs->dpp_program_regamma_pwl(dpp, NULL, OPP_REGAMMA_BYPASS);
 
-	log_tf(stream->ctx,
-			stream->out_transfer_func,
-			dpp->regamma_params.hw_points_num);
+	if (stream != NULL && stream->ctx != NULL &&
+			stream->out_transfer_func != NULL) {
+		log_tf(stream->ctx,
+				stream->out_transfer_func,
+				dpp->regamma_params.hw_points_num);
+	}
 
 	return true;
 }