drm/amd/display: Reset gamma to NULL after release

Signed-off-by: Anthony Koo <anthony.koo@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/color/color.c

@@ -1748,8 +1748,10 @@ bool mod_color_remove_sink(struct mod_color *mod_color,
 
 	for (i = 0; i < core_color->num_sinks; i++) {
 		if (core_color->caps[i].sink == sink) {
-			if (core_color->state[i].gamma)
+			if (core_color->state[i].gamma) {
 				dc_gamma_release(core_color->state[i].gamma);
+				core_color->state[i].gamma = NULL;
+			}
 
 			/* To remove this sink, shift everything after down */
 			for (j = i; j < core_color->num_sinks - 1; j++) {