SchedulerBackup: handle null value returned by listFiles

additionally, improve logging

scheduler/scheduler-api/src/main/java/org/ow2/proactive/scheduler/common/util/ZipUtils.java

@@ -145,12 +145,16 @@ public class ZipUtils extends FileUtils {
             if (dirobject.isDirectory()) {
                 File[] fileList = dirobject.listFiles();
                 // Loop through the files
-                for (int i = 0; i < fileList.length; i++) {
-                    if (fileList[i].isDirectory()) {
-                        zipDirectory(fileList[i].getPath(), iBaseFolderLength, zos, crc);
-                    } else if (fileList[i].isFile()) {
-                        zipFile(fileList[i].getPath(), iBaseFolderLength, zos, crc);
+                if (fileList != null) {
+                    for (int i = 0; i < fileList.length; i++) {
+                        if (fileList[i].isDirectory()) {
+                            zipDirectory(fileList[i].getPath(), iBaseFolderLength, zos, crc);
+                        } else if (fileList[i].isFile()) {
+                            zipFile(fileList[i].getPath(), iBaseFolderLength, zos, crc);
+                        }
                     }
+                } else {
+                    logger.warn("Problem accessing folder: " + dirobject);
                 }
             } else {
                 throw new IOException(directoryName + " is not a directory.");

scheduler/scheduler-server/src/main/java/org/ow2/proactive/scheduler/core/SchedulerBackupRunner.java

@@ -128,7 +128,12 @@ public class SchedulerBackupRunner implements Runnable {
                                            .map(target -> (new File(PASchedulerProperties.SCHEDULER_HOME.getValueAsString(),
                                                                     target)).getAbsolutePath())
                                            .toArray(String[]::new);
-            ZipUtils.zip(foldersToZip, backupFile, null);
+            LOGGER.info("Backup of the following folders : " + Arrays.toString(foldersToZip));
+            try {
+                ZipUtils.zip(foldersToZip, backupFile, null);
+            } catch (Exception e) {
+                LOGGER.error("Error when performing backup", e);
+            }
         } else {
             LOGGER.error("Cannot save a backup because backup configuredDestination folder does not exist: " +
                          configuredDestination);