added code to handle cases where the funding tree is not existing

dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/dump/community/SparkPrepareResultProject.java

@@ -135,12 +135,17 @@ public class SparkPrepareResultProject implements Serializable {
 								.orElse(null),
 						Optional
 								.ofNullable(op.getFundingtree())
-					.map(
-						value -> value
+								.map(value -> {
+									List<Funder> tmp = value
 											.stream()
 											.map(ft -> getFunder(ft.getValue()))
-							.collect(Collectors.toList())
-							.get(0))
+											.collect(Collectors.toList());
+									if (tmp.size() > 0) {
+										return tmp.get(0);
+									} else {
+										return null;
+									}
+								})
 								.orElse(null));
 
 		Optional<DataInfo> di = Optional.ofNullable(op.getDataInfo());