drm/amd/display: Check for NULL when creating gamma struct

[Wjy&How] Some stress test is causing unexpected memory allocation
failure. This prevents null dereference but there will likely be problems
later, hard to gracefully handle memalloc fail for critical objects.
Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Acked-by: Reza Amini <Reza.Amini@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -40,11 +40,14 @@ static void construct(struct dc_context *ctx, struct dc_plane_state *plane_state
 	plane_state->ctx = ctx;
 
 	plane_state->gamma_correction = dc_create_gamma();
-	plane_state->gamma_correction->is_identity = true;
+	if (plane_state->gamma_correction != NULL)
+		plane_state->gamma_correction->is_identity = true;
 
 	plane_state->in_transfer_func = dc_create_transfer_func();
-	plane_state->in_transfer_func->type = TF_TYPE_BYPASS;
-	plane_state->in_transfer_func->ctx = ctx;
+	if (plane_state->in_transfer_func != NULL) {
+		plane_state->in_transfer_func->type = TF_TYPE_BYPASS;
+		plane_state->in_transfer_func->ctx = ctx;
+	}
 }
 
 static void destruct(struct dc_plane_state *plane_state)