Index: trunk/src/org/openstreetmap/josm/data/imagery/vectortile/mapbox/MVTTile.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/imagery/vectortile/mapbox/MVTTile.java	(revision 18155)
+++ trunk/src/org/openstreetmap/josm/data/imagery/vectortile/mapbox/MVTTile.java	(revision 18156)
@@ -1,4 +1,13 @@
 // License: GPL. For details, see LICENSE file.
 package org.openstreetmap.josm.data.imagery.vectortile.mapbox;
+
+import java.awt.image.BufferedImage;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
 
 import org.openstreetmap.gui.jmapviewer.Tile;
@@ -13,12 +22,4 @@
 import org.openstreetmap.josm.tools.ListenerList;
 import org.openstreetmap.josm.tools.Logging;
-
-import java.awt.image.BufferedImage;
-import java.io.IOException;
-import java.io.InputStream;
-import java.util.Collection;
-import java.util.HashSet;
-import java.util.List;
-import java.util.stream.Collectors;
 
 /**
@@ -68,5 +69,5 @@
                 return mvtLayer;
             }).collect(Collectors.toCollection(HashSet::new));
-            this.extent = layers.stream().map(Layer::getExtent).max(Integer::compare).orElse(Layer.DEFAULT_EXTENT);
+            this.extent = layers.stream().filter(Objects::nonNull).mapToInt(Layer::getExtent).max().orElse(Layer.DEFAULT_EXTENT);
             if (this.getData() != null) {
                 this.finishLoading();