RANGER-3806: Group's users mapping entry failing whenever primary key auto-increment is not set to 1 in db

(cherry picked from commit ef64136)

Author: pradeepagrawal8184

security-admin/src/main/java/org/apache/ranger/service/XGroupUserService.java

@@ -305,8 +305,11 @@ private void updateGroupUserMappings() {
 					xxGroupUser = new XXGroupUser();
 					groupUserMappingExists = false;
 				}
-				xxGroupUser.setAddedByUserId(createdByUserId);
-				xxGroupUser.setUpdatedByUserId(createdByUserId);
+				XXPortalUser xXPortalUser = daoManager.getXXPortalUser().getById(createdByUserId);
+				if (xXPortalUser != null) {
+					xxGroupUser.setAddedByUserId(createdByUserId);
+					xxGroupUser.setUpdatedByUserId(createdByUserId);
+				}
 
 				if (groupUserMappingExists) {
 					xxGroupUser = getDao().update(xxGroupUser);