FIXUP: Avoid a ConcurrentModificationException (fixes #74)

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

src/main/java/org/openstreetmap/josm/plugins/mapwithai/backend/GetDataRunnable.java

@@ -498,7 +498,7 @@ public class GetDataRunnable extends RecursiveTask<DataSet> {
         final DataSet dataSet = new DataSet();
         dataSet.setUploadPolicy(UploadPolicy.DISCOURAGED);
 
-        MapWithAILayerInfo.instance.getLayers().parallelStream().forEach(map -> {
+        new ArrayList<>(MapWithAILayerInfo.instance.getLayers()).parallelStream().forEach(map -> {
             try {
                 Bounds bound = new Bounds(bbox.getBottomRight());
                 bound.extend(bbox.getTopLeft());