src/os/unix/ngx_readv_chain.c:194: error: Null Dereference
  pointer `iov` last assigned on line 181 could be null and is dereferenced at line 194, column 13.

src/os/unix/ngx_readv_chain.c:170:1: start of procedure ngx_readv_chain()
168. #else /* ! NGX_HAVE_KQUEUE */
169. 
170. ssize_t
     ^
171. ngx_readv_chain(ngx_connection_t *c, ngx_chain_t *chain)
172. {

src/os/unix/ngx_readv_chain.c:180:5: 
178.     struct iovec  *iov, iovs[NGX_IOVS];
179. 
180.     prev = NULL;
         ^
181.     iov = NULL;
182.     size = 0;

src/os/unix/ngx_readv_chain.c:181:5: 
179. 
180.     prev = NULL;
181.     iov = NULL;
         ^
182.     size = 0;
183. 

src/os/unix/ngx_readv_chain.c:182:5: 
180.     prev = NULL;
181.     iov = NULL;
182.     size = 0;
         ^
183. 
184.     vec.elts = iovs;

src/os/unix/ngx_readv_chain.c:184:5: 
182.     size = 0;
183. 
184.     vec.elts = iovs;
         ^
185.     vec.nelts = 0;
186.     vec.size = sizeof(struct iovec);

src/os/unix/ngx_readv_chain.c:185:5: 
183. 
184.     vec.elts = iovs;
185.     vec.nelts = 0;
         ^
186.     vec.size = sizeof(struct iovec);
187.     vec.nalloc = NGX_IOVS;

src/os/unix/ngx_readv_chain.c:186:5: 
184.     vec.elts = iovs;
185.     vec.nelts = 0;
186.     vec.size = sizeof(struct iovec);
         ^
187.     vec.nalloc = NGX_IOVS;
188.     vec.pool = c->pool;

src/os/unix/ngx_readv_chain.c:187:5: 
185.     vec.nelts = 0;
186.     vec.size = sizeof(struct iovec);
187.     vec.nalloc = NGX_IOVS;
         ^
188.     vec.pool = c->pool;
189. 

src/os/unix/ngx_readv_chain.c:188:5: 
186.     vec.size = sizeof(struct iovec);
187.     vec.nalloc = NGX_IOVS;
188.     vec.pool = c->pool;
         ^
189. 
190.     /* coalesce the neighbouring bufs */

src/os/unix/ngx_readv_chain.c:192:12: Loop condition is true. Entering loop body
190.     /* coalesce the neighbouring bufs */
191. 
192.     while (chain) {
                ^
193.         if (prev == chain->buf->last) {
194.             iov->iov_len += chain->buf->end - chain->buf->last;

src/os/unix/ngx_readv_chain.c:193:13: Taking true branch
191. 
192.     while (chain) {
193.         if (prev == chain->buf->last) {
                 ^
194.             iov->iov_len += chain->buf->end - chain->buf->last;
195. 

src/os/unix/ngx_readv_chain.c:194:13: 
192.     while (chain) {
193.         if (prev == chain->buf->last) {
194.             iov->iov_len += chain->buf->end - chain->buf->last;
                 ^
195. 
196.         } else {
