SAK-26151 FileUserDirectoryProvider should pass failed searches back.

When a problem occurs with one of the providers in the FilterUserDirectoryProvider it should pass that error back up to the caller. Before this it was causing a stack trace with a NPE

git-svn-id: https://source.sakaiproject.org/svn/providers/trunk@308665 66ffb92e-73f9-0310-93c1-f5514f145a0a

providers/federating/src/java/org/sakaiproject/provider/user/FilterUserDirectoryProvider.java

@@ -574,7 +574,13 @@ public List<UserEdit> searchExternalUsers(String criteria, int first, int last,
 				m_logger.debug("searchExternalUsers() criteria=" + criteria);
 			}
 
-			users.addAll(extSearchUDP.searchExternalUsers(criteria, first, last, factory));
+			List<UserEdit> searchExternalUsers = extSearchUDP.searchExternalUsers(criteria, first, last, factory);
+			if (searchExternalUsers != null) {
+				users.addAll(searchExternalUsers);
+			} else {
+				// When something goes wrong with the search we want to pass this back up the stack.
+				return null;
+			}
 		}
 
 		if ( nextProvider instanceof ExternalUserSearchUDP) {
@@ -584,7 +590,13 @@ public List<UserEdit> searchExternalUsers(String criteria, int first, int last,
 				m_logger.debug("nextProvider searchExternalUsers() criteria=" + criteria);
 			}
 
-			users.addAll(extSearchUDP.searchExternalUsers(criteria, first, last, factory));
+			List<UserEdit> searchExternalUsers = extSearchUDP.searchExternalUsers(criteria, first, last, factory);
+			if (searchExternalUsers != null) {
+				users.addAll(searchExternalUsers);
+			} else {
+				// When something goes wrong with the search we want to pass this back up the stack.
+				return null;
+			}
 		}
 
 		return users;