How to support indefinite integrals on mathquill.js?

Question

I'm building a web app based on mathquill and I'd like to support indefinite integrals. However, when I type \int, the output I see is this:

Ideally, the two gray blank spaces shouldn't appear. I tried editing the html render of integrals on mathquill source code, which is the following:

LatexCmds['int'] =
LatexCmds.integral = P(SummationNotation, function(_, super_) {
  _.init = function() {
    var htmlTemplate =
      '<span class="mq-int mq-non-leaf">'
    +   '<big>&int;</big>'
    +   '<span class="mq-supsub mq-non-leaf">'
    +     '<span class="mq-sup"><span class="mq-sup-inner">&1</span></span>'
    +     '<span class="mq-sub">&0</span>'
    +     '<span style="display:inline-block;width:0">&#8203</span>'
    +   '</span>'
    + '</span>'
    ;
    Symbol.prototype.init.call(this, '\\int ', htmlTemplate);
  };
  // FIXME: refactor rather than overriding
  _.createLeftOf = MathCommand.p.createLeftOf;
});

And transformed it into this one:

LatexCmds['int'] =
LatexCmds.integral = P(SummationNotation, function(_, super_) {
  _.init = function() {
    var htmlTemplate =
      '<span class="mq-int mq-non-leaf">'
    +   '<big>&int;</big>'
    + '</span>'
    ;
    Symbol.prototype.init.call(this, '\\int ', htmlTemplate);
  };
  // FIXME: refactor rather than overriding
  _.createLeftOf = MathCommand.p.createLeftOf;
});

Which technically should get rid of those gray blanks. However, the problem persists, and I don't know how to fix it.