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:577:1: start of procedure ngx_http_get_indexed_variable()
  575. 
  576. 
  577. ngx_http_variable_value_t *
       ^
  578. ngx_http_get_indexed_variable(ngx_http_request_t *r, ngx_uint_t index)
  579. {

src/http/ngx_http_variables.c:583:5: 
  581.     ngx_http_core_main_conf_t  *cmcf;
  582. 
  583.     cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
           ^
  584. 
  585.     if (cmcf->variables.nelts <= index) {

src/http/ngx_http_variables.c:585:9: Taking false branch
  583.     cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
  584. 
  585.     if (cmcf->variables.nelts <= index) {
               ^
  586.         ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
  587.                       "unknown variable index: %ui", index);

src/http/ngx_http_variables.c:591:9: Taking false branch
  589.     }
  590. 
  591.     if (r->variables[index].not_found || r->variables[index].valid) {
               ^
  592.         return &r->variables[index];
  593.     }

src/http/ngx_http_variables.c:591:42: Taking false branch
  589.     }
  590. 
  591.     if (r->variables[index].not_found || r->variables[index].valid) {
                                                ^
  592.         return &r->variables[index];
  593.     }

src/http/ngx_http_variables.c:595:5: 
  593.     }
  594. 
  595.     v = cmcf->variables.elts;
           ^
  596. 
  597.     if (ngx_http_variable_depth == 0) {

src/http/ngx_http_variables.c:597:9: Taking false branch
  595.     v = cmcf->variables.elts;
  596. 
  597.     if (ngx_http_variable_depth == 0) {
               ^
  598.         ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
  599.                       "cycle while evaluating variable \"%V\"",

src/http/ngx_http_variables.c:604:5: 
  602.     }
  603. 
  604.     ngx_http_variable_depth--;
           ^
  605. 
  606.     if (v[index].get_handler(r, &r->variables[index], v[index].data)

src/http/ngx_http_variables.c:606:9: Taking false branch
  604.     ngx_http_variable_depth--;
  605. 
  606.     if (v[index].get_handler(r, &r->variables[index], v[index].data)
               ^
  607.         == NGX_OK)
  608.     {

src/http/ngx_http_variables.c:618:5: 
  616.     }
  617. 
  618.     ngx_http_variable_depth++;
           ^
  619. 
  620.     r->variables[index].valid = 0;

src/http/ngx_http_variables.c:620:5: 
  618.     ngx_http_variable_depth++;
  619. 
  620.     r->variables[index].valid = 0;
           ^
  621.     r->variables[index].not_found = 1;
  622. 

src/http/ngx_http_variables.c:621:5: 
  619. 
  620.     r->variables[index].valid = 0;
  621.     r->variables[index].not_found = 1;
           ^
  622. 
  623.     return NULL;

src/http/ngx_http_variables.c:623:5: 
  621.     r->variables[index].not_found = 1;
  622. 
  623.     return NULL;
           ^
  624. }
  625. 

src/http/ngx_http_variables.c:624:1: return from a call to ngx_http_get_indexed_variable
  622. 
  623.     return NULL;
  624. }
       ^
  625. 
  626. 

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'
