Not nullable dataKey in DropDown break selectedOption property

[m1n0s]

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[x] bug report
[ ] feature request
[ ] support request => Please do not submit support request here, instead see https://forum.primefaces.org/viewforum.php?f=57

Current behavior
Next compiled code of Dropdown component doesn't work properly

key: "findOptionIndex",
    value: function findOptionIndex(value) {
      var index = -1;

      if (this.props.options) {
        for (var i = 0; i < this.props.options.length; i++) {
          var optionValue = this.getOptionValue(this.props.options[i]);

          if (value === null && optionValue == null || _ObjectUtils.default.equals(value, optionValue, this.props.dataKey)) {
            index = i;
            break;
          }
        }
      }

      return index;
    }

if value and optionValue are primitive strings and dataKey is not null which is a not rare case I think. In this scenarion selectedOption in render will be not correct.

Expected behavior
Selected option according to value prop.

The PR is ready actually. I just wanted to create issue to follow your procedures.