Socket address of closed socket should be null (support PHP 8)

The previous code works just fine on PHP 7 and older. PHP 8 adds
stricter type checks for closed socket resources, so the underlying
function now throws a `TypeError`. This can be avoided by first checking
if the socket resource is still valid (not closed). This works across
all PHP versions and also helps with avoiding some uneeded error
suppression operators.

Author: clue

src/Connection.php

@@ -138,12 +138,20 @@ public function handleClose()
 
     public function getRemoteAddress()
     {
-        return $this->parseAddress(@\stream_socket_get_name($this->stream, true));
+        if (!\is_resource($this->stream)) {
+            return null;
+        }
+
+        return $this->parseAddress(\stream_socket_get_name($this->stream, true));
     }
 
     public function getLocalAddress()
     {
-        return $this->parseAddress(@\stream_socket_get_name($this->stream, false));
+        if (!\is_resource($this->stream)) {
+            return null;
+        }
+
+        return $this->parseAddress(\stream_socket_get_name($this->stream, false));
     }
 
     private function parseAddress($address)