acl: Don't assert-crash if removing all rights.

--HG--
branch : HEAD

diff --git a/src/plugins/acl/acl-backend-vfile.c b/src/plugins/acl/acl-backend-vfile.c
index d39b1b0b03227d0a9dfbd7272f61442f9622f1e0..ca880563fadd062323951867b93592443a158905 100644 (file)
--- a/src/plugins/acl/acl-backend-vfile.c
+++ b/src/plugins/acl/acl-backend-vfile.c
@@ -901,7 +901,8 @@ static bool modify_right_list(pool_t pool,
                                array_append(&rights, &old_rights[i], 1);
                }
                new_rights = &null;
-               modify_rights = array_idx(&rights, 0);
+               modify_rights = array_count(&rights) == 0 ? NULL :
+                       array_idx(&rights, 0);
                acl_rights_merge(pool, &new_rights, modify_rights, TRUE);
                break;
        case ACL_MODIFY_MODE_ADD: