Index: trunk/src/org/openstreetmap/josm/data/validation/tests/PowerLines.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/tests/PowerLines.java	(revision 18674)
+++ trunk/src/org/openstreetmap/josm/data/validation/tests/PowerLines.java	(revision 18675)
@@ -131,5 +131,10 @@
         for (int i = 0; i < w.getNodesCount() - 1; i++) {
             final WaySegment es1 = new WaySegment(w, i);
-            CrossingWays.getSegments(this.cellSegmentsWater, es1.getFirstNode(), es1.getSecondNode()).forEach(list -> list.add(es1));
+            final Node first = es1.getFirstNode();
+            final Node second = es1.getSecondNode();
+
+            if (first.isLatLonKnown() && second.isLatLonKnown()) {
+                CrossingWays.getSegments(this.cellSegmentsWater, first, second).forEach(list -> list.add(es1));
+            }
         }
     }
Index: trunk/src/org/openstreetmap/josm/tools/Geometry.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/Geometry.java	(revision 18674)
+++ trunk/src/org/openstreetmap/josm/tools/Geometry.java	(revision 18675)
@@ -939,5 +939,5 @@
      */
     public static EastNorth getCentroid(List<? extends INode> nodes) {
-        return getCentroidEN(nodes.stream().map(INode::getEastNorth).collect(Collectors.toList()));
+        return getCentroidEN(nodes.stream().filter(INode::isLatLonKnown).map(INode::getEastNorth).collect(Collectors.toList()));
     }
 
@@ -955,4 +955,6 @@
         } else if (size == 2) {
             return nodes.get(0).getCenter(nodes.get(1));
+        } else if (size == 0) {
+            return null;
         }
 
Index: trunk/test/unit/org/openstreetmap/josm/data/validation/tests/PowerLinesTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/data/validation/tests/PowerLinesTest.java	(revision 18674)
+++ trunk/test/unit/org/openstreetmap/josm/data/validation/tests/PowerLinesTest.java	(revision 18675)
@@ -2,4 +2,5 @@
 package org.openstreetmap.josm.data.validation.tests;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -7,12 +8,14 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.RegisterExtension;
+import org.openstreetmap.josm.TestUtils;
 import org.openstreetmap.josm.data.coor.LatLon;
 import org.openstreetmap.josm.data.osm.DataSet;
 import org.openstreetmap.josm.data.osm.Node;
+import org.openstreetmap.josm.data.osm.Relation;
+import org.openstreetmap.josm.data.osm.RelationMember;
 import org.openstreetmap.josm.data.osm.TagMap;
 import org.openstreetmap.josm.data.osm.Way;
-import org.openstreetmap.josm.testutils.JOSMTestRules;
 import org.openstreetmap.josm.testutils.annotations.BasicPreferences;
+import org.openstreetmap.josm.testutils.annotations.Projection;
 
 /**
@@ -21,10 +24,8 @@
  */
 @BasicPreferences
+@Projection
 class PowerLinesTest {
     private PowerLines powerLines;
     private DataSet ds;
-
-    @RegisterExtension
-    static JOSMTestRules josmTestRules = new JOSMTestRules().projection();
 
     @BeforeEach
@@ -119,3 +120,13 @@
         assertFalse(powerLines.getErrors().isEmpty());
     }
+
+    /**
+     * Ensure that incomplete relations don't cause problems
+     */
+    @Test
+    void testNonRegression22684() {
+        final Relation powerLine = TestUtils.newRelation("natural=water water=river",
+                new RelationMember("", TestUtils.newWay("", new Node(), new Node())));
+        assertDoesNotThrow(() -> this.powerLines.visit(powerLine));
+    }
 }
Index: trunk/test/unit/org/openstreetmap/josm/tools/GeometryTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/tools/GeometryTest.java	(revision 18674)
+++ trunk/test/unit/org/openstreetmap/josm/tools/GeometryTest.java	(revision 18675)
@@ -2,8 +2,10 @@
 package org.openstreetmap.josm.tools;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -18,7 +20,5 @@
 import java.util.stream.Stream;
 
-import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
@@ -39,17 +39,12 @@
 import org.openstreetmap.josm.data.projection.Projections;
 import org.openstreetmap.josm.io.OsmReader;
-import org.openstreetmap.josm.testutils.JOSMTestRules;
+import org.openstreetmap.josm.testutils.annotations.BasicPreferences;
 
 /**
  * Unit tests of {@link Geometry} class.
  */
+@BasicPreferences
+@org.openstreetmap.josm.testutils.annotations.Projection
 class GeometryTest {
-    /**
-     * Primitives need preferences and projection.
-     */
-    @RegisterExtension
-    @SuppressFBWarnings(value = "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD")
-    static JOSMTestRules test = new JOSMTestRules().preferences().projection();
-
     /**
      * Test of {@link Geometry#getLineLineIntersection} method.
@@ -578,3 +573,17 @@
         assertEquals(angle, Math.toDegrees(original.bearing(actual)), 0.000_001);
     }
+
+    /**
+     * A non-regression test for an issue found during the investigation of #22684 (see comment:3 by GerdP)
+     */
+    @Test
+    void testNonRegression22684() {
+        final EastNorth centroid1 = assertDoesNotThrow(() -> Geometry.getCentroid(Collections.singletonList(new Node())));
+        assertNull(centroid1);
+        final EastNorth centroid2 = assertDoesNotThrow(() -> Geometry.getCentroid(Arrays.asList(new Node(LatLon.ZERO), new Node())));
+        assertTrue(new EastNorth(0, 0).equalsEpsilon(centroid2, 1e-9));
+        final EastNorth centroid3 = assertDoesNotThrow(
+                () -> Geometry.getCentroid(Arrays.asList(new Node(LatLon.ZERO), new Node(), new Node(LatLon.ZERO))));
+        assertTrue(new EastNorth(0, 0).equalsEpsilon(centroid3, 1e-9));
+    }
 }