src/os/unix/ngx_readv_chain.c:199: error: Null Dereference
  pointer `iov` last assigned on line 186 could be null and is dereferenced at line 199, column 13.

src/os/unix/ngx_readv_chain.c:175:1: start of procedure ngx_readv_chain()
173. #else /* ! NGX_HAVE_KQUEUE */
174. 
175. ssize_t
     ^
176. ngx_readv_chain(ngx_connection_t *c, ngx_chain_t *chain)
177. {

src/os/unix/ngx_readv_chain.c:185:5: 
183.     struct iovec  *iov, iovs[NGX_IOVS];
184. 
185.     prev = NULL;
         ^
186.     iov = NULL;
187.     size = 0;

src/os/unix/ngx_readv_chain.c:186:5: 
184. 
185.     prev = NULL;
186.     iov = NULL;
         ^
187.     size = 0;
188. 

src/os/unix/ngx_readv_chain.c:187:5: 
185.     prev = NULL;
186.     iov = NULL;
187.     size = 0;
         ^
188. 
189.     vec.elts = iovs;

src/os/unix/ngx_readv_chain.c:189:5: 
187.     size = 0;
188. 
189.     vec.elts = iovs;
         ^
190.     vec.nelts = 0;
191.     vec.size = sizeof(struct iovec);

src/os/unix/ngx_readv_chain.c:190:5: 
188. 
189.     vec.elts = iovs;
190.     vec.nelts = 0;
         ^
191.     vec.size = sizeof(struct iovec);
192.     vec.nalloc = NGX_IOVS;

src/os/unix/ngx_readv_chain.c:191:5: 
189.     vec.elts = iovs;
190.     vec.nelts = 0;
191.     vec.size = sizeof(struct iovec);
         ^
192.     vec.nalloc = NGX_IOVS;
193.     vec.pool = c->pool;

src/os/unix/ngx_readv_chain.c:192:5: 
190.     vec.nelts = 0;
191.     vec.size = sizeof(struct iovec);
192.     vec.nalloc = NGX_IOVS;
         ^
193.     vec.pool = c->pool;
194. 

src/os/unix/ngx_readv_chain.c:193:5: 
191.     vec.size = sizeof(struct iovec);
192.     vec.nalloc = NGX_IOVS;
193.     vec.pool = c->pool;
         ^
194. 
195.     /* coalesce the neighbouring bufs */

src/os/unix/ngx_readv_chain.c:197:12: Loop condition is true. Entering loop body
195.     /* coalesce the neighbouring bufs */
196. 
197.     while (chain) {
                ^
198.         if (prev == chain->buf->last) {
199.             iov->iov_len += chain->buf->end - chain->buf->last;

src/os/unix/ngx_readv_chain.c:198:13: Taking true branch
196. 
197.     while (chain) {
198.         if (prev == chain->buf->last) {
                 ^
199.             iov->iov_len += chain->buf->end - chain->buf->last;
200. 

src/os/unix/ngx_readv_chain.c:199:13: 
197.     while (chain) {
198.         if (prev == chain->buf->last) {
199.             iov->iov_len += chain->buf->end - chain->buf->last;
                 ^
200. 
201.         } else {
