Length of a radio group being returned as undefined when there is only one radio button in the group

The radio.length value returns 'undefined' when there is only one value in a radio group.  

I know it is not normal to have just one value in the radio group, but I find myself in that situation where the number of radio buttons in the group depends on the output of a query.

Anyone knows how I can work around this issue.

JAVASCRIPT FUNCTION:
 
<script type="text/javascript">
	function getRadioValue(radio) {
	    for(i=0; i<radio.length; i++) {
	        if(radio[i].checked) return radio[i].value;
	    }
	    return 0;
	}
</script>

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