API / Batch editing / On preview mode, return exception

When using preview mode, no report or exception are returned and it is hard to track what is wrong with XPath or XML snippet.

Report exception directly.

services/src/main/java/org/fao/geonet/api/records/editing/BatchEditsApi.java

@@ -299,6 +299,9 @@ private Pair<SimpleMetadataProcessingReport, Element> applyBatchEdits(
                     }
                 } catch (Exception e) {
                     report.addMetadataError(record, e);
+                    if (previewOnly) {
+                        throw e;
+                    }
                 }
                 report.incrementProcessedRecords();
             }