drm/amd/display: Add Null check for DPP resource

[what and why]
Check whether dpp resource pointer is null in advance and return early
if so.
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Martin Leung <martin.leung@amd.com>
Signed-off-by: Gabe Teeger <gabe.teeger@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -945,7 +945,7 @@ static void adjust_recout_for_visual_confirm(struct rect *recout,
 	struct dc *dc = pipe_ctx->stream->ctx->dc;
 	int dpp_offset, base_offset;
 
-	if (dc->debug.visual_confirm == VISUAL_CONFIRM_DISABLE)
+	if (dc->debug.visual_confirm == VISUAL_CONFIRM_DISABLE || !pipe_ctx->plane_res.dpp)
 		return;
 
 	dpp_offset = pipe_ctx->stream->timing.v_addressable / VISUAL_CONFIRM_DPP_OFFSET_DENO;