error: register custom invalid error
#define FLB_ERR_CFG_FLUSH 20
#define FLB_ERR_CFG_FLUSH_CREATE 21
#define FLB_ERR_CFG_FLUSH_REGISTER 22
+#define FLB_ERR_CUSTOM_INVALID 49
#define FLB_ERR_INPUT_INVALID 50
#define FLB_ERR_INPUT_UNDEF 51
#define FLB_ERR_INPUT_UNSUP 52
