Fix possible possible NPE with merging duplicate ways

Signed-off-by: Taylor Smock <taylor.smock@kaart.com>

src/main/java/org/openstreetmap/josm/plugins/mapwithai/commands/MergeDuplicateWays.java

@@ -66,6 +66,8 @@ public class MergeDuplicateWays extends Command {
                 filterDataSet(getAffectedDataSet(), commands);
             } else if (way1 != null && way2 == null) {
                 checkForDuplicateWays(way1, commands);
+            } else if (way1 == null) {
+                checkForDuplicateWays(way2, commands);
             } else {
                 Command command = checkForDuplicateWays(way1, way2);
                 if (command != null) {