drm/amd/display: Add check for num of entries in gamma

This check avoids potential bugs related to gamma.

Signed-off-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1580,7 +1580,8 @@ bool mod_color_calculate_degamma_params(struct dc_transfer_func *input_tf,
 	/* we can use hardcoded curve for plain SRGB TF */
 	if (input_tf->type == TF_TYPE_PREDEFINED &&
 			input_tf->tf == TRANSFER_FUNCTION_SRGB &&
-			(!mapUserRamp && ramp->type == GAMMA_RGB_256))
+			(!mapUserRamp &&
+			(ramp->type == GAMMA_RGB_256 || ramp->num_entries == 0)))
 		return true;
 
 	input_tf->type = TF_TYPE_DISTRIBUTED_POINTS;