src/http/modules/ngx_http_userid_filter_module.c:474: error: Null Dereference
  pointer `vv` last assigned on line 472 could be null and is dereferenced at line 474, column 13.

src/http/modules/ngx_http_userid_filter_module.c:454:1: start of procedure ngx_http_userid_create_uid()
452. 
453. 
454. static ngx_int_t
     ^
455. ngx_http_userid_create_uid(ngx_http_request_t *r, ngx_http_userid_ctx_t *ctx,
456.     ngx_http_userid_conf_t *conf)

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

src/http/modules/ngx_http_userid_filter_module.c:470:9: Taking true branch
468.     }
469. 
470.     if (ctx->uid_got[3] != 0) {
             ^
471. 
472.         vv = ngx_http_get_indexed_variable(r, ngx_http_userid_reset_index);

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

src/http/ngx_http_variables.c:386:1: start of procedure ngx_http_get_indexed_variable()
  384. 
  385. 
  386. ngx_http_variable_value_t *
       ^
  387. ngx_http_get_indexed_variable(ngx_http_request_t *r, ngx_uint_t index)
  388. {

src/http/ngx_http_variables.c:392:5: 
  390.     ngx_http_core_main_conf_t  *cmcf;
  391. 
  392.     cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
           ^
  393. 
  394.     if (cmcf->variables.nelts <= index) {

src/http/ngx_http_variables.c:394:9: Taking false branch
  392.     cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
  393. 
  394.     if (cmcf->variables.nelts <= index) {
               ^
  395.         ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
  396.                       "unknown variable index: %d", index);

src/http/ngx_http_variables.c:400:9: Taking false branch
  398.     }
  399. 
  400.     if (r->variables[index].not_found || r->variables[index].valid) {
               ^
  401.         return &r->variables[index];
  402.     }

src/http/ngx_http_variables.c:400:42: Taking false branch
  398.     }
  399. 
  400.     if (r->variables[index].not_found || r->variables[index].valid) {
                                                ^
  401.         return &r->variables[index];
  402.     }

src/http/ngx_http_variables.c:404:5: 
  402.     }
  403. 
  404.     v = cmcf->variables.elts;
           ^
  405. 
  406.     if (v[index].get_handler(r, &r->variables[index], v[index].data)

src/http/ngx_http_variables.c:406:9: Taking false branch
  404.     v = cmcf->variables.elts;
  405. 
  406.     if (v[index].get_handler(r, &r->variables[index], v[index].data)
               ^
  407.         == NGX_OK)
  408.     {

src/http/ngx_http_variables.c:416:5: 
  414.     }
  415. 
  416.     r->variables[index].valid = 0;
           ^
  417.     r->variables[index].not_found = 1;
  418. 

src/http/ngx_http_variables.c:417:5: 
  415. 
  416.     r->variables[index].valid = 0;
  417.     r->variables[index].not_found = 1;
           ^
  418. 
  419.     return NULL;

src/http/ngx_http_variables.c:419:5: 
  417.     r->variables[index].not_found = 1;
  418. 
  419.     return NULL;
           ^
  420. }
  421. 

src/http/ngx_http_variables.c:420:1: return from a call to ngx_http_get_indexed_variable
  418. 
  419.     return NULL;
  420. }
       ^
  421. 
  422. 

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