http2: fix session[kSession] undefined issue

`finishSessionDestroy` session cleanup when already done.

PR-URL: #24547
Fixes: #24546
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ouyang Yadong <oyydoibh@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/internal/http2/core.js

@@ -1989,6 +1989,7 @@ class Http2Stream extends Duplex {
       // attempt to gracefully close the session.
       const state = this[kState];
       if (this.headersSent &&
+          this[kSession] &&
           this[kSession][kType] === NGHTTP2_SESSION_SERVER &&
           !(state.flags & STREAM_FLAGS_HAS_TRAILERS) &&
           !state.didRead &&

test/parallel/test-http2-server-session-destroy.js

@@ -0,0 +1,20 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const h2 = require('http2');
+
+const server = h2.createServer();
+server.listen(0, common.localhostIPv4, common.mustCall(() => {
+  const afterConnect = common.mustCall((session) => {
+    session.request({ ':method': 'POST' }).end(common.mustCall(() => {
+      session.destroy();
+      server.close();
+    }));
+  });
+
+  const port = server.address().port;
+  const host = common.localhostIPv4;
+  h2.connect('http://' + host + ':' + port, afterConnect);
+}));