Index: trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java	(revision 12707)
+++ trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java	(revision 12709)
@@ -661,5 +661,5 @@
             this.currentLayer = matchingLayers.stream().filter(
                     l -> l.tileMatrixSet.identifier.equals(defaultLayer.getTileMatrixSet()))
-                    .findFirst().orElse(null);
+                    .findFirst().orElse(matchingLayers.get(0));
             this.tileProjection = proj;
         } else if (matchingLayers.size() == 1) {