src/http/modules/ngx_http_userid_filter_module.c:475: error: Null Dereference
  pointer `vv` last assigned on line 473 could be null and is dereferenced at line 475, column 13.

src/http/modules/ngx_http_userid_filter_module.c:455:1: start of procedure ngx_http_userid_create_uid()
453. 
454. 
455. static ngx_int_t
     ^
456. ngx_http_userid_create_uid(ngx_http_request_t *r, ngx_http_userid_ctx_t *ctx,
457.     ngx_http_userid_conf_t *conf)

src/http/modules/ngx_http_userid_filter_module.c:467:9: Taking false branch
465. #endif
466. 
467.     if (ctx->uid_set[3] != 0) {
             ^
468.         return NGX_OK;
469.     }

src/http/modules/ngx_http_userid_filter_module.c:471:9: Taking true branch
469.     }
470. 
471.     if (ctx->uid_got[3] != 0) {
             ^
472. 
473.         vv = ngx_http_get_indexed_variable(r, ngx_http_userid_reset_index);

src/http/modules/ngx_http_userid_filter_module.c:473:9: 
471.     if (ctx->uid_got[3] != 0) {
472. 
473.         vv = ngx_http_get_indexed_variable(r, ngx_http_userid_reset_index);
             ^
474. 
475.         if (vv->len == 0 || (vv->len == 1 && vv->data[0] == '0')) {

src/http/ngx_http_variables.c:480:1: start of procedure ngx_http_get_indexed_variable()
  478. 
  479. 
  480. ngx_http_variable_value_t *
       ^
  481. ngx_http_get_indexed_variable(ngx_http_request_t *r, ngx_uint_t index)
  482. {

src/http/ngx_http_variables.c:486:5: 
  484.     ngx_http_core_main_conf_t  *cmcf;
  485. 
  486.     cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
           ^
  487. 
  488.     if (cmcf->variables.nelts <= index) {

src/http/ngx_http_variables.c:488:9: Taking false branch
  486.     cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
  487. 
  488.     if (cmcf->variables.nelts <= index) {
               ^
  489.         ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
  490.                       "unknown variable index: %ui", index);

src/http/ngx_http_variables.c:494:9: Taking false branch
  492.     }
  493. 
  494.     if (r->variables[index].not_found || r->variables[index].valid) {
               ^
  495.         return &r->variables[index];
  496.     }

src/http/ngx_http_variables.c:494:42: Taking false branch
  492.     }
  493. 
  494.     if (r->variables[index].not_found || r->variables[index].valid) {
                                                ^
  495.         return &r->variables[index];
  496.     }

src/http/ngx_http_variables.c:498:5: 
  496.     }
  497. 
  498.     v = cmcf->variables.elts;
           ^
  499. 
  500.     if (v[index].get_handler(r, &r->variables[index], v[index].data)

src/http/ngx_http_variables.c:500:9: Taking false branch
  498.     v = cmcf->variables.elts;
  499. 
  500.     if (v[index].get_handler(r, &r->variables[index], v[index].data)
               ^
  501.         == NGX_OK)
  502.     {

src/http/ngx_http_variables.c:510:5: 
  508.     }
  509. 
  510.     r->variables[index].valid = 0;
           ^
  511.     r->variables[index].not_found = 1;
  512. 

src/http/ngx_http_variables.c:511:5: 
  509. 
  510.     r->variables[index].valid = 0;
  511.     r->variables[index].not_found = 1;
           ^
  512. 
  513.     return NULL;

src/http/ngx_http_variables.c:513:5: 
  511.     r->variables[index].not_found = 1;
  512. 
  513.     return NULL;
           ^
  514. }
  515. 

src/http/ngx_http_variables.c:514:1: return from a call to ngx_http_get_indexed_variable
  512. 
  513.     return NULL;
  514. }
       ^
  515. 
  516. 

src/http/modules/ngx_http_userid_filter_module.c:475:13: 
473.         vv = ngx_http_get_indexed_variable(r, ngx_http_userid_reset_index);
474. 
475.         if (vv->len == 0 || (vv->len == 1 && vv->data[0] == '0')) {
                 ^
476. 
477.             if (conf->mark == '\0'
