src/os/unix/ngx_readv_chain.c:200: error: Null Dereference
  pointer `iov` last assigned on line 187 could be null and is dereferenced at line 200, column 13.

src/os/unix/ngx_readv_chain.c:176:1: start of procedure ngx_readv_chain()
174. #else /* ! NGX_HAVE_KQUEUE */
175. 
176. ssize_t
     ^
177. ngx_readv_chain(ngx_connection_t *c, ngx_chain_t *chain)
178. {

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

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

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

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

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

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

src/os/unix/ngx_readv_chain.c:193:5: 
191.     vec.nelts = 0;
192.     vec.size = sizeof(struct iovec);
193.     vec.nalloc = NGX_IOVS;
         ^
194.     vec.pool = c->pool;
195. 

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

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

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

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