From 12ba057b4f74a6ef4989d0ceb4075ef74bcc6ea2 Mon Sep 17 00:00:00 2001
From: ISSOtm <eldredhabert0@gmail.com>
Date: Tue, 11 Oct 2022 21:39:32 +0200
Subject: [PATCH] Check that colour slot is non-empty before checking for
 gray-ness

This is otherwise UB, and trips a GLIBCXX assertion (when enabled).
---
 src/gfx/process.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/gfx/process.cpp b/src/gfx/process.cpp
index d19dc72c..8b0ec650 100644
--- a/src/gfx/process.cpp
+++ b/src/gfx/process.cpp
@@ -142,7 +142,7 @@ public:
 		}
 		uint8_t bins = 0;
 		for (auto const &color : colors) {
-			if (color->isTransparent()) {
+			if (!color.has_value() || color->isTransparent()) {
 				continue;
 			}
 			if (!color->isGray()) {