murun: Remove unused resource stack causing NULL pointer read

[PietroCarrara]

This is a simple bugfix: mutool run had a stack for PDF objects that was only being read from, not written to. This caused a NULL/garbage pointer read.

There were two ways this could be fixed, in my mind:

• Actually inserting pdf objects into the stack
• Removing the whole thing;

I picked the 2nd option because:

• It's simpler
• When we create PDF objects to pass to JS (ffi_pushobj), we already register functions to drop them. So I believe there's no need for the cleanup that existed before.

Below, there's a simple case to reproduce the bug:

Reproducing

• Download blank-form.pdf or any PDF with a XForm Object.
• Run mutool run bug.js blank-form.pdf

bug.js:

function main() {
  var input = Document.openDocument(scriptArgs[0]);

  for (var i = 0; i < input.countPages(); i++) {
    var page = input.loadPage(i);
    page.process({
      op_Do_form: function () {
        print("Hello from JS!");
      },
    });
  }
}

if (scriptArgs.length !== 1) {
  print("usage: mutool run input.pdf");
} else {
  main();
}

Expected output

The program prints Hello from JS! for each Form XObject.

Actual output

The program segfaults.