Fix null pointer crash in Listener.getsockname() when called without arguments

When `getsockname()` was called without an out-object argument (e.g.
`Bun.listen(...).getsockname()`), the first argument defaulted to
`undefined`. This was then passed to `JSC__JSValue__putBunString` in
C++, where `getObject()` returned null, causing a null pointer
dereference in `putDirect`.

Fix: when no object argument is provided, create a new empty object to
populate and return it. When an out-object is provided, preserve the
existing behavior of populating it in-place and returning undefined.

https://claude.ai/code/session_01PxYrYFseM3UutPg2C5AKM8

src/bun.js/api/bun/socket/Listener.zig

@@ -850,7 +850,9 @@ pub fn getsockname(this: *Listener, globalThis: *jsc.JSGlobalObject, callFrame:
         return .js_undefined;
     }
 
-    const out = callFrame.argumentsAsArray(1)[0];
+    const arg = callFrame.argumentsAsArray(1)[0];
+    const has_out = arg.isObject();
+    const out = if (has_out) arg else JSValue.createEmptyObject(globalThis, 3);
     const socket = this.listener.uws;
 
     var buf: [64]u8 = [_]u8{0} ** 64;
@@ -872,7 +874,7 @@ pub fn getsockname(this: *Listener, globalThis: *jsc.JSGlobalObject, callFrame:
     out.put(globalThis, bun.String.static("family"), family_js);
     out.put(globalThis, bun.String.static("address"), address_js);
     out.put(globalThis, bun.String.static("port"), port_js);
-    return .js_undefined;
+    return if (has_out) .js_undefined else out;
 }
 
 pub fn jsAddServerName(global: *jsc.JSGlobalObject, callframe: *jsc.CallFrame) bun.JSError!JSValue {

test/js/bun/net/tcp-server.test.ts

@@ -57,6 +57,46 @@ it("remoteAddress works", async () => {
   await prom;
 });
 
+it("getsockname without arguments should not crash", () => {
+  using server = Bun.listen({
+    socket: {
+      open() {},
+      close() {},
+      data() {},
+    },
+    port: 0,
+    hostname: "127.0.0.1",
+  });
+
+  const result = server.getsockname();
+  expect(result).toEqual({
+    family: "IPv4",
+    address: "127.0.0.1",
+    port: server.port,
+  });
+});
+
+it("getsockname with an out object populates it", () => {
+  using server = Bun.listen({
+    socket: {
+      open() {},
+      close() {},
+      data() {},
+    },
+    port: 0,
+    hostname: "127.0.0.1",
+  });
+
+  const out: Record<string, unknown> = {};
+  const result = server.getsockname(out);
+  expect(result).toBeUndefined();
+  expect(out).toEqual({
+    family: "IPv4",
+    address: "127.0.0.1",
+    port: server.port,
+  });
+});
+
 it("should not allow invalid tls option", () => {
   [1, "string", Symbol("symbol")].forEach(value => {
     expect(() => {