drm/amd/display: Guard against NULL link encoder in log hw state

[Why & How]
Check lenc is not NULL since dynamic link encoder assignment could
end up assigning a NULL link encoder.
Reviewed-by: Michael Strauss <Michael.Strauss@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@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/dcn10/dcn10_hw_sequencer.c

@@ -444,7 +444,7 @@ void dcn10_log_hw_state(struct dc *dc,
 
 		struct link_enc_state s = {0};
 
-		if (lenc->funcs->read_state) {
+		if (lenc && lenc->funcs->read_state) {
 			lenc->funcs->read_state(lenc, &s);
 			DTN_INFO("[%-3d]: %-12d %-22d %-22d %-25d\n",
 				i,