From 6c0d1e0f15baf9930a48ebeeb2ba204f3ae932f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20K=C3=B6ppe?= <tkoeppe@google.com>
Date: Thu, 21 Jun 2018 12:45:54 +0100
Subject: [PATCH] [QuantOctree.c] Remove erroneous attempt to average over an
 empty range.

---
 src/libImaging/QuantOctree.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/libImaging/QuantOctree.c b/src/libImaging/QuantOctree.c
index e18ab3c65..018dfe1d9 100644
--- a/src/libImaging/QuantOctree.c
+++ b/src/libImaging/QuantOctree.c
@@ -259,6 +259,10 @@ subtract_color_buckets(ColorCube cube, ColorBucket buckets, long nBuckets) {
    Pixel p;
    for (i=0; i<nBuckets; i++) {
       subtrahend = &buckets[i];
+
+      // If the subtrahend contains no buckets, there is nothing to subtract.
+      if (subtrahend->count == 0) continue;
+
       avg_color_from_color_bucket(subtrahend, &p);
       minuend = color_bucket_from_cube(cube, &p);
       minuend->count -= subtrahend->count;