Fix crash in HTMLInputElement::setupDateTimeChooserParameters

LayoutTests/fast/forms/calendar-picker/datepicker-crash-after-keydown.html

+<input id="month" type="month"</div>
+<script>
+if (window.testRunner) {
+  testRunner.dumpAsText();
+}
+function openPicker(input) {
+  sendKey(input, "Down", false, true);
+  finishTest();
+}
+function sendKey(input, keyName, ctrlKey, altKey) {
+  var event = document.createEvent('KeyboardEvent');
+  event.initKeyboardEvent('keydown', true, true, document.defaultView, keyName, 0, ctrlKey, altKey);
+  input.dispatchEvent(event);
+}
+openPicker(document.getElementById('month'), finishTest);
+function finishTest() {
+  document.body.innerText = 'PASS (not crashed)';
+}
+</script>