fix(client): divide by zero error when DNS returns no addrs (#3355)

Consider addrs length is 0.

From issue: seanmonstar/reqwest#2003

src/client/connect/http.rs

@@ -521,7 +521,7 @@ struct ConnectingTcpRemote {
 
 impl ConnectingTcpRemote {
  fn new(addrs: dns::SocketAddrs, connect_timeout: Option<Duration>) -> Self {
- let connect_timeout = connect_timeout.map(|t| t / (addrs.len() as u32));
+ let connect_timeout = connect_timeout.map(|t| t.checked_div(addrs.len() as u32)).flatten();
 
  Self {
  addrs,