From b658367d7f98ad3531c00f528bffbdb4fb8135f3 Mon Sep 17 00:00:00 2001
From: Gabriel Selzer <gjselzer@wisc.edu>
Date: Wed, 20 Apr 2022 13:14:58 -0500
Subject: [PATCH] Ensure empty label sets don't throw exceptions

---
 .../java/net/imglib2/labeling/DefaultLabelingIOService.java    | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/main/java/net/imglib2/labeling/DefaultLabelingIOService.java b/src/main/java/net/imglib2/labeling/DefaultLabelingIOService.java
index 88284b8..f99b376 100644
--- a/src/main/java/net/imglib2/labeling/DefaultLabelingIOService.java
+++ b/src/main/java/net/imglib2/labeling/DefaultLabelingIOService.java
@@ -140,7 +140,8 @@ private <S, T, I extends IntegerType<I>> ImgLabeling<T, I> buildImgLabelingAndIm
     }
 
     private <T, S> void createLabelsets(LabelingMapping<T> labelingMapping, LabelingData<T, S> labelingData) {
-        if (labelingMapping.getLabels().stream().findFirst().get() instanceof Integer) {
+        Optional<T> optional = labelingMapping.getLabels().stream().findFirst();
+        if (optional.isPresent() && optional.get() instanceof Integer) {
             Map<String, Set<Integer>> labels = new HashMap<>();
             for (int i = 0; i < labelingMapping.numSets(); i++) {
                 labels.put(Integer.toString(i), (Set<Integer>) labelingMapping.labelsAtIndex(i));