ssh: unwrap -> error handling

The port number is guaranteed to be set in the config parser,
just like for the host and user, so the unwrap is "OK", but it's
less brittle to handle the error consistent with the others here.

Cargo.lock

@@ -1841,7 +1841,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "10463d9ff00a2a068db14231982f5132edebad0d7660cd956a1c30292dbcbfbd"
 dependencies = [
  "aho-corasick",
- "bstr 0.2.16",
+ "bstr 0.2.17",
  "fnv",
  "log",
  "regex",

wezterm-ssh/src/session.rs

@@ -125,7 +125,11 @@ impl SessionInner {
             .get("user")
             .ok_or_else(|| anyhow!("username not present in config"))?
             .to_string();
-        let port = self.config.get("port").unwrap().parse::<u16>()?;
+        let port = self
+            .config
+            .get("port")
+            .ok_or_else(|| anyhow!("port is always set in config loader"))?
+            .parse::<u16>()?;
         let remote_address = format!("{}:{}", hostname, port);
 
         let tcp: TcpStream = if let Some(proxy_command) =