update

This reverts commit 722ac3aa5a.

src/bun.js/api/bun/subprocess.zig

@@ -590,7 +590,7 @@ pub fn onProcessExit(this: *Subprocess, process: *Process, status: bun.spawn.Sta
     var existing_stdin_value = jsc.JSValue.zero;
     if (this_jsvalue != .zero) {
         if (jsc.Codegen.JSSubprocess.stdinGetCached(this_jsvalue)) |existing_value| {
-            if (existing_value.isCell()) {
+            if (existing_stdin_value.isCell()) {
                 if (stdin == null) {
                     // TODO: review this cast
                     stdin = @ptrCast(@alignCast(jsc.WebCore.FileSink.JSSink.fromJS(existing_value)));